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High pressure warnings

Printed From: Enfield-Rifles.com
Category: Enfields
Forum Name: Ishapore Enfields
Forum Description: Let's see those Indian Enfields!
URL: http://www.enfield-rifles.com/forum_posts.asp?TID=10895
Printed Date: November 28 2020 at 8:30am
Software Version: Web Wiz Forums 12.01 - http://www.webwizforums.com


Topic: High pressure warnings
Posted By: Frameman 1
Subject: High pressure warnings
Date Posted: October 14 2020 at 4:09am
I fired these rounds yesterday. I used new Hornady 308 cases with CCI 200 primers , Hornady 165 gr, SST bullets with 42 gr. Of IMR 4895 powder. I thought this load would be fine but the signs say otherwise.
Any thoughts? 


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There are no Americans in Baghdad!!



Replies:
Posted By: Goosic
Date Posted: October 14 2020 at 5:10am
According to Hodgdon and using Fed 210M primers, they indicate a starting load of IMR 4895 at 40.7grns. The psi is only 49,200 with a velocity of 2584. 
It gives a maximum compressed load of 45.5grns, a psi of 58,800 and a velocity of 2745.
You might be experiencing an issue of not enough powder. The line around the fired case is well above where a case separation occurs and may have something to do with the way the chamber was reamed.
What rifle are you experiencing this issue with?


Posted By: The Armourer
Date Posted: October 14 2020 at 6:19am
As this is posted in the Ishapore section of the forum I'll assume that that is what we are talking about.

Remember that these rifles were only proof tested based on the 144 gr NATO bullet, and even then the Proof testing was fudged to get them to pass.

I am no expert on pressures but listen to those with much more experience than I

It is not ideal to use heavier weight bullets.

Heavier bullets accelerate slower than lighter bullets. Slower bullets means less space behind them which means higher pressure, which means faster powder burn which means even more pressure.

There is s discussion about the 2A / 2A1's on another forum where Brian d**k* suggests that nothing other than NATO 144gr should be used - he had one to repair where someone decided to load up to M118 LR specs with a 175gr bullet and wondered why the bolt disintegrated.

*Brian (BDL Ltd) is possibly one of the most experienced armourers and repairers of LE's in the USA.


Posted By: The Armourer
Date Posted: October 14 2020 at 6:35am
Originally posted by Goosic Goosic wrote:

According to Hodgdon and using Fed 210M primers, they indicate a starting load of IMR 4895 at 40.7grns. The psi is only 49,200 with a velocity of 2584. 
It gives a maximum compressed load of 45.5grns, a psi of 58,800 and a velocity of 2745.
You might be experiencing an issue of not enough powder. The line around the fired case is well above where a case separation occurs and may have something to do with the way the chamber was reamed.
What rifle are you experiencing this issue with?

As I have said - I am no expert on loading and looking to learn.

If the OP is using 42gr  and the 'manuals' say a minimum load is 40.7gr (is that for 308 ?) why would the OP's 42 gr be 'an issue of not enough powder' ?

Would the bullet being 15% heavier than the rifle was designed for not also cause pressure problems ?
Would the fact that 7.62 cases are thicker and have less volume than 308 cases not cause a rise in pressures as well ?




Posted By: Honkytonk
Date Posted: October 14 2020 at 6:36am
A while ago I was wondering asking a question on minimum/maximum loads, but didn't as I thought it might be too obvious. We all know the potential dangers of loading to maximum or over with these older rifles. Actually, any rifle for that matter. Other than the bullet stopping half way down the barrel, what are other potential dangers of loading below recommended powder charges? Thanks!


Posted By: Frameman 1
Date Posted: October 14 2020 at 7:18am
the rifle used was an Ishapore 2A1. Cut down by Gibbs most likely into a tanker carbine.

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There are no Americans in Baghdad!!


Posted By: Goosic
Date Posted: October 14 2020 at 7:23am
Originally posted by The Armourer The Armourer wrote:

Originally posted by Goosic Goosic wrote:

According to Hodgdon and using Fed 210M primers, they indicate a starting load of IMR 4895 at 40.7grns. The psi is only 49,200 with a velocity of 2584. 
It gives a maximum compressed load of 45.5grns, a psi of 58,800 and a velocity of 2745.
You might be experiencing an issue of not enough powder. The line around the fired case is well above where a case separation occurs and may have something to do with the way the chamber was reamed.
What rifle are you experiencing this issue with?

As I have said - I am no expert on loading and looking to learn.

If the OP is using 42gr  and the 'manuals' say a minimum load is 40.7gr (is that for 308 ?) why would the OP's 42 gr be 'an issue of not enough powder' ?

Would the bullet being 15% heavier than the rifle was designed for not also cause pressure problems ?
Would the fact that 7.62 cases are thicker and have less volume than 308 cases not cause a rise in pressures as well ?


I misread his original post The Armourer . My apologies to you and yours.



Posted By: The Armourer
Date Posted: October 14 2020 at 8:16am
Originally posted by Goosic Goosic wrote:

Originally posted by The Armourer The Armourer wrote:

Originally posted by Goosic Goosic wrote:

According to Hodgdon and using Fed 210M primers, they indicate a starting load of IMR 4895 at 40.7grns. The psi is only 49,200 with a velocity of 2584. 
It gives a maximum compressed load of 45.5grns, a psi of 58,800 and a velocity of 2745.
You might be experiencing an issue of not enough powder. The line around the fired case is well above where a case separation occurs and may have something to do with the way the chamber was reamed.
What rifle are you experiencing this issue with?

As I have said - I am no expert on loading and looking to learn.

If the OP is using 42gr  and the 'manuals' say a minimum load is 40.7gr (is that for 308 ?) why would the OP's 42 gr be 'an issue of not enough powder' ?

Would the bullet being 15% heavier than the rifle was designed for not also cause pressure problems ?
Would the fact that 7.62 cases are thicker and have less volume than 308 cases not cause a rise in pressures as well ?


I misread his original post The Armourer . My apologies to you and yours.



No problem, I thought I was just misunderstanding it.

I'm trying to increase my re-loading knowledge - I only reload for my 303's using the wack-a-mole system.


Posted By: Goosic
Date Posted: October 14 2020 at 8:49am
Originally posted by The Armourer The Armourer wrote:


Remember that these rifles were only proof tested based on the 144 gr NATO bullet, and even then the Proof testing was fudged to get them to pass.

There is s discussion about the 2A / 2A1's on another forum where Brian d**k* suggests that nothing other than NATO 144gr should be used - he had one to repair where someone decided to load up to M118 LR specs with a 175gr bullet and wondered why the bolt disintegrated.

*Brian (BDL Ltd) is possibly one of the most experienced armourers and repairers of LE's in the USA.
 
It is interesting that you brought up the M118LR.
I have been using the updated M852 special ball ammunition to the original M118. It is handloads consisting of the 168grn BTHP, 41.0grns of IMR4064, and GM215M primers. I also use for the really long range stuff, the MK316 MOD O special ball. That consists of a 175gr BTHP,  41.7grns of IMR4064 and GM215M primers as well. Both rounds have been extensively used in my No4Mk1/2 with the 2A1barrel.  No noticable pressure issues,no blown primers,no case separation, and no issue with extraction of a spent round. I have witnessed on a few occasions, a primer that has backed itself out of the pocket from an undercharged round. That in conjunction with a light firing pin strike. 


Posted By: Frameman 1
Date Posted: October 14 2020 at 9:39am
This is the load data I was using from Hornady 

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There are no Americans in Baghdad!!


Posted By: Goosic
Date Posted: October 14 2020 at 9:54am
You are right on the cusp of a max charge. Hornady has a starting weight of 35.0grns of IMR4895. Always start with the minimum and work your way up.


Posted By: Frameman 1
Date Posted: October 14 2020 at 10:44am
you are correct. I jumped ahead a bit too far

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There are no Americans in Baghdad!!


Posted By: Zed
Date Posted: October 14 2020 at 11:39am
As a side note. The rifle bolt mentioned by Armourer; that was discussed on another forum came from an L42A1. These No4 type are stronger bodies than the SMLE type. Yet they can still fail if you load heavy bullets with hot loads. 
I think that keeping the bullet velocity similar to that of the standard .303 is probably adviseable if using bullets of a similar weight.


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It's nice to be important, but it's more important to be nice!


Posted By: britrifles
Date Posted: October 14 2020 at 5:49pm
From the Hodgdon web site:



H4895 powder performs exceptionally well with reduced loads (less than published minimums).   Some powders will not ignite and burn consistently with loads less than minimum, not a problem with H4895.  

My approach has been to load the .308/7.62 converted No. 4 rifles to within .303 British pressures, can’t go wrong with this.  

The No. 4 action was never designed to 7.62 NATO or .308 Winchester.  It was designed to use the .303 British Mk 7 cartridge.  If you want your rifles to last for 30,000 rounds, keep loads well below the .303 British maximum average pressure of 45.000 CUP (preferably below 40,000 CUP).  

The thrust loads on the bolt are a function of the chamber pressure and area at the rear of the chamber, the .308 is slightly larger in diameter than the .303 at the base of the cartridge.  


 










Posted By: Frameman 1
Date Posted: October 14 2020 at 6:05pm
Going forward, my loads will be towards the lower end of range provided by the manufacturer of whatever components I’m using.

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There are no Americans in Baghdad!!


Posted By: Goosic
Date Posted: October 14 2020 at 8:34pm
Just a suggestion.  Start with 36.0grns of IMR4895,  stay with the 165grn SST bullets as well as the CCI 200 primers. Your velocity will not exceed 2200 fps, the pressure limits will never be reached, and barrel wear will be reduced greatly. 


Posted By: The Armourer
Date Posted: October 15 2020 at 12:02am
Originally posted by britrifles britrifles wrote:

From the Hodgdon web site:



H4895 powder performs exceptionally well with reduced loads (less than published minimums).   Some powders will not ignite and burn consistently with loads less than minimum, not a problem with H4895.  

My approach has been to load the .308/7.62 converted No. 4 rifles to within .303 British pressures, can’t go wrong with this.  

The No. 4 action was never designed to 7.62 NATO or .308 Winchester.  It was designed to use the .303 British Mk 7 cartridge.  If you want your rifles to last for 30,000 rounds, keep loads well below the .303 British maximum average pressure of 45.000 CUP (preferably below 40,000 CUP).  

The thrust loads on the bolt are a function of the chamber pressure and area at the rear of the chamber, the .308 is slightly larger in diameter than the .303 at the base of the cartridge.  


 










Interesting that that loading gives the same pressure as the maximum service pressure for the standard NATO round




Posted By: britrifles
Date Posted: October 15 2020 at 4:55am
Hodgdon lists load data for the .308 Winchester and .308 Service Rifle.  The .308 Service Rifle data is intended for self loading Service rifles chambered in 7.62/.308 such as the M14 and M1A.  

This is the load data for .308 Service Rifle for 168 gr SMK with H4895. 




Posted By: The Armourer
Date Posted: October 15 2020 at 9:02am



Originally posted by britrifles britrifles wrote:

Hodgdon lists load data for the .308 Winchester and .308 Service Rifle.  The .308 Service Rifle data is intended for self loading Service rifles chambered in 7.62/.308 such as the M14 and M1A.  

This is the load data for .308 Service Rifle for 168 gr SMK with H4895. 



That suggest that the OP loading with 42 gr was right at MAX load (Max = 42.3gr)

Unsurprising that there are signs of over-pressure.


Posted By: britrifles
Date Posted: October 15 2020 at 12:29pm
Flattened primers will often indicate excessive headspace, particularly with new or full length sized cases.

I don’t think your load produced pressures above maximum of 45,000 CUP for the .303 British cartridge, and well within maximum for 7.62 NATO.  However, if headspace on your rifle is on the high side or near maximum you will get primer flattening.  As pressure builds on firing the cartridge, the primer is first pushed Out of the primer pocket and back up against the bolt head to take up the “head clearance” (space between the case head and back of the bolt when locking lugs are fully seated in the receiver).  It does not take much pressure to do this.   As chamber pressure continues to build, the case will then slam hard against the back of the bolt after it looses its grip on the chamber walls and/or stretches.  That impact force is what flattens the primer.  

Some flattening is normal for loads that are within maximum published data.   If the radiused edge of the primer cup is completely square (90 deg) you should check headspace.  If headspace is good, then inspect the fired primers after shooting neck sized cases that have been fired in this rifle, they should not be severely flattened.  If they are, your load is excessive. 





Posted By: The Armourer
Date Posted: October 15 2020 at 1:53pm
Originally posted by britrifles britrifles wrote:

Flattened primers will often indicate excessive headspace, particularly with new or full length sized cases.

 If headspace is good, then inspect the fired primers after shooting neck sized cases that have been fired in this rifle, they should not be severely flattened.  If they are, your load is excessive. 




What should the headspace be for the Ishapore 7.62 (it isn't the same as 308) and where on the neck do you take the headspace measurement ?

There are more than a dozen different 7.62 'Go' and the same amount of 'No-Go' gauges within NATO.
All with different dimensions and used for differing purposes in different rifles.

Ishapore developed their own headspace for their 2A / 2A1 rifles which is similar to one of the NATO gauges.


An extract of a long presentation given by Peter Laidler in 2008


Now for the biggie, the 7.62’s. The basic principle of headspacing hasn’t changed here but the practicalities have. Whereas before, on our rimmed .303” rifles we measured the GO NO-GO distance between the front face of the bolt and the rear face of the barrel, it’s all changed for the rimless 7.62mm NATO caliber rifles. Now we have to measure from the front face of the bolt to the cartridge seating at the neck. Well, that’s all pretty clear then ….., except that the neck is tapered so where EXACTLY on that neck do you take your GO, 1.628” and NO-GO 1.635 measurement from? Even if I told you it’d make no difference whatsoever because without the specialist measuring and more importantly, the calibration equipment, you’d still be none the wiser. The trouble with this is that you’ve got to take the word of the manufacturer of the gauge. And exactly where does HE take HIS measurement from but more importantly, WHO does he get them from. geting difficult isn't it?

Let me give you an example. My GO gauge gives you a close/GO reading of 1.628 but Bloggs & Co gauge may give you a GO reading of 1.575” for the same 7.62mm caliber. How can there be a difference of .053” between the two when they are identical? Well, it’s simple really. Our STANAG gauges are measured from one diameter around the neck while Bloggs & Co are taken from a different but larger diameter .053” further to the rear! That is really all I want to say about that.


Ishapore actually call their gauges "Low" (Go) and High (No-Go) so if you find some marked this way  - they may just be 'Ishy' gauges.


Posted By: britrifles
Date Posted: October 15 2020 at 2:32pm
Both of my 7.62 converted No. 4 rifles (done at Long Branch, Ontario) have headspace that falls between commercial (SAAMI) Go and No Go.  I would start there.  If the bolt closes on the SAAMI NO GO, I would start to worry.  If it closed on a SAAMI Field gage, I wouldn’t shoot the rifle. 

It doesn’t have to be complicated.  




Posted By: The Armourer
Date Posted: October 15 2020 at 3:20pm
Originally posted by britrifles britrifles wrote:

Both of my 7.62 converted No. 4 rifles (done at Long Branch, Ontario) have headspace that falls between commercial (SAAMI) Go and No Go.  I would start there.  If the bolt closes on the SAAMI NO GO, I would start to worry.  If it closed on a SAAMI Field gage, I wouldn’t shoot the rifle. 

It doesn’t have to be complicated.  



But in this case we are talking about Ishapore 2A / 2A1 rifles and the headspace as determined by Ishapore, NOT NATO, and NOT SAAMI.


Posted By: Goosic
Date Posted: October 15 2020 at 3:25pm
The Armourer 

[/QUOTE]
What should the headspace be for the Ishapore 7.62 (it isn't the same as 308) and where on the neck do you take the headspace measurement ?
[/QUOTE]
I asked myself this exact question when I started my conversions using the 2A1 barrel knowing full well I was going to use once fired 7.62x51mm NATO brass full length resized in 308 dies. I have a 308 Field gauge @1.638" so, the choice was obvious.  I did what I had to do and ended up with a rifle that has extremely tight tolerances as far as headspacing goes. 
The fired cases show no signs of stretching, and the primers did not flatten. The 308 Winchester is not entirely identical to the 7.62x51mm NATO, owing to differences in tolerances; therefore, some commercial rifles will not handle military ammunition. 
   The OP started out with a charge weight right on the edge of maximum and the result was a stretched case and flattened primers. He ultimately needs to start over and load to the minimum starting charge weight.  If he observes flattened primers and excessive case stretching then make the assumption that headspacing needs to be corrected. 


Posted By: Goosic
Date Posted: October 15 2020 at 3:37pm
Originally posted by The Armourer The Armourer wrote:


But in this case we are talking about Ishapore 2A / 2A1 rifles and the headspace as determined by Ishapore, NOT NATO, and NOT SAAMI.
Headspace WAS determined by Ishapore when Ishapore was in full swing producing 2A/2A1 rifles. Who determines headspacing now? The cartridge used is still a 7.62x51mm NATO cartridge, or a derivative thereof.  Therefore, headspace should be determined by a competent armourer or gunsmith due to Ishapore not actively participating in  the production process of 2A/2A1 rifles any longer correct? As long as the rifle headspacing falls within the prescribed tolerances set forth by the infamous Peter Laidler, everything should be as he is ofte quoted as saying," Easy Peasy Lemon Sqeezy"...


Posted By: britrifles
Date Posted: October 15 2020 at 6:58pm
Originally posted by The Armourer The Armourer wrote:

Originally posted by britrifles britrifles wrote:

Both of my 7.62 converted No. 4 rifles (done at Long Branch, Ontario) have headspace that falls between commercial (SAAMI) Go and No Go.  I would start there.  If the bolt closes on the SAAMI NO GO, I would start to worry.  If it closed on a SAAMI Field gage, I wouldn’t shoot the rifle. 

It doesn’t have to be complicated.  



But in this case we are talking about Ishapore 2A / 2A1 rifles and the headspace as determined by Ishapore, NOT NATO, and NOT SAAMI.

Yes, but we are reloading it with .308 Winchester components and load tables.


Posted By: The Armourer
Date Posted: October 16 2020 at 12:39am
Originally posted by britrifles britrifles wrote:

Originally posted by The Armourer The Armourer wrote:

Originally posted by britrifles britrifles wrote:

Both of my 7.62 converted No. 4 rifles (done at Long Branch, Ontario) have headspace that falls between commercial (SAAMI) Go and No Go.  I would start there.  If the bolt closes on the SAAMI NO GO, I would start to worry.  If it closed on a SAAMI Field gage, I wouldn’t shoot the rifle. 

It doesn’t have to be complicated.  



But in this case we are talking about Ishapore 2A / 2A1 rifles and the headspace as determined by Ishapore, NOT NATO, and NOT SAAMI.

Yes, but we are reloading it with .308 Winchester components and load tables.

That was exactly my point.

7.62 headspace is actually 13 thou greater than 308 headspace, so how can you use 308 headspace gauges without knowing where the dimension is taken.

It may well be that your 308 headspace gauges 'work' for you simply because the 'measurement' is taken in a different position on the taper of the neck. But how do you know ?


Posted By: Frameman 1
Date Posted: October 16 2020 at 2:41am
I’m in deep water with the headspace measurements. I personally have no way of accurately measuring headspace. Can a “reasonable “ bolt face to case gap measurement be accomplished? And how to do this?

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There are no Americans in Baghdad!!


Posted By: The Armourer
Date Posted: October 16 2020 at 4:25am
Originally posted by Frameman 1 Frameman 1 wrote:

I’m in deep water with the headspace measurements. I personally have no way of accurately measuring headspace. Can a “reasonable “ bolt face to case gap measurement be accomplished? And how to do this?

No.

303 is a rimmed case that you can measure from the bolt face to the rim.

308 is a non-rimmed cartridge and the headspace is taken part way down the taper of the chamber.

It cannot be measure against the bolt head and the case rim.


Posted By: Frameman 1
Date Posted: October 16 2020 at 5:08am
I understand that the registers for the case seating are taken from different parts of the case but the fact remains that in both calibers the case contacts the chamber wall to stop its forward motion.
That being said, shouldn’t the bolt to case gap still be a relevant measurement?


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There are no Americans in Baghdad!!


Posted By: britrifles
Date Posted: October 16 2020 at 6:17am
If we shoot new .308 or 7.62 NATO ammunition, or full length sized cases with .308 dies, case external dimensions are the same.  Ergo, a .308 SAAMI gage will provide a satisfactory indication of the chamber headspace to that standard that is safe for these cartridges.  Yes, military 7.62 chambers are generally longer than SAAMI .308 chambers but not the other way around, so you will be safe using SAAMI gages.

The other way to check this is to use a case headspace gage.  I use the Hornady gage to measure the case headspace after firing and set my FL reloading die to push the shoulder back .002 to .004 inches and no more.  You can measure new cases as a reference and determine how much the case is elongating to fit the chamber.  

Although we don’t know the exact chamber dimensions used by Ishapore, we do know that .308 brass can be safely fired if the chamber measures within SAAMI .308 specs. Both my No. 4 converted rifles do, the bolt is a long way from closing on the .308 NO GO gage. 

 








Posted By: The Armourer
Date Posted: October 16 2020 at 7:34am
Originally posted by Frameman 1 Frameman 1 wrote:

I understand that the registers for the case seating are taken from different parts of the case but the fact remains that in both calibers the case contacts the chamber wall to stop its forward motion.
That being said, shouldn’t the bolt to case gap still be a relevant measurement?

With a 303 there should be a minimum gap between the case rim and the front of the bolt head. If there is a large gap then a different bolt head should be fitted.
In reality a small gap is always likely to exist but head 'clearance' should be minimised.

Changing from 'quality' cases such as PPU or Military cases to the thinner rimmed SAAMI cases means that this 'clearance' space is increased, effectively increasing your headspace.
If your headspace (on a 303) is close to the maximum, your headspace can be actually pushed over the top by using 'thin rimmed' cases, or reduced by using 'thick rimmed cases'

Take the example of a rifle 'just' passing the 0.074" No-Go test and has a headspce of 0.072".

If you use a SAAMI spec case that has a Rim thickness of 0.057" then you now have a gap of 0.015" between the rear of the case rim and the front edge of the bolt head. On firing the case expands binding on the chamber, the rear of the case can move backwards by 15 thou before it gets any resistance so, stretching the case and ending up with a weak point at the 'case web' and the infamous "Enfield Ring Of Death". 
This ring is not the fault of the Enfield 'generous chamber' but of the owner using thin rimmed cases without checking their effect on the headspace and head clearance.

An interesting little Gif (By a poster called Parashooter)





If you took a cross section of a 7.62 chamber you would see that the cartridge case 'fouls' the neck taper on the chanber - this is what stops the cartridge moving forward and where the headspace is normally taken.
On a 303 the cartridge is stopped moving forward by the rim hitting the breech. You can see in the above Gif that prior to firing, the case does not touch the chamber at all, and is the reason for the 'trick' of using a rubber ring (hair band etc) to centre the case in the chamber - otherwise it just sits in the bottom of the chanber.


On firing (both 303 and 7.62) expand to 'fit the space' and then, as long as their elastic limit has not been exceeded, will revert back to (almost) their original dimensions.


Posted By: britrifles
Date Posted: October 16 2020 at 8:05am
One thing for certain is that military rifles don’t consider cartridge case reloading.  As long as there is a margin on case head ruptures, it is of no concern if brass elongates.  Not so for us who reload.  We want headspace to be tight for long case life.

The No. 4 Long Branch 7.62 converted rifles were built for target shooting purposes which likely explains the relatively tight headspace that conforms to SAAMI .308 Win specs.  I suspect that’s how they set the headspace on these rifles even though they would be used with Canadian issue 7.62 NATO ammunition.  Not being a machine gun where cartridge feeding reliability is a primary concern, they likely saw no reason to ream the chambers out to NATO specs intended for MG use.   I’ve got a 1960’s DCRA instruction sheet on converting .303 barrels to fire the 7.62 cartridge and these instructions call out the use of a .308 Win reamer.  

I have no idea what Ishapore did for chamber headspace on their rifles, but if the OPs rifle is indeed to the high side of 7.62 NATO specs, and a new .308 case was used, a flattened primer is going to occur, likely with light loads as well.  Also pretty severe case headspace elongation.  That would also happen with a 7.62 NATO case. 








Posted By: The Armourer
Date Posted: October 16 2020 at 12:43pm
Originally posted by britrifles britrifles wrote:

.  

I have no idea what Ishapore did for chamber headspace on their rifles, but if the OPs rifle is indeed to the high side of 7.62 NATO specs, and a new .308 case was used, a flattened primer is going to occur, likely with light loads as well.  Also pretty severe case headspace elongation.  That would also happen with a 7.62 NATO case. 



The Ishapore headspace is : 


Low (Go) 1.633
High (NoGo) 1.642

But knowing that is not much help unless you know where on the 'slope' that figure is taken.
You could have 308Win gauges with exactly the same dimension but taken further up/down the slope.

The only was to be sure is to obtain NATO gauges with those measurements - but - there aren't any.

The nearest (and ones folk rebuilding Ishapore's use) are the L1A1 gauges at :
Go 1.6325" 
NoGo 1.643". 

There is no such thing as 'Field' in military headspace gauges.

It's a bit higher that you would normally have expected from a bolt action rifle BUT, it is still the generally accepted ~ .010" between go and no-go.

Can you find any 'proper' military issue L1A1 gauges ?

The 308Win headspace gauges are 

Go 1.630"
NoGo 1.634"








Posted By: Goosic
Date Posted: October 16 2020 at 12:46pm


Posted By: britrifles
Date Posted: October 16 2020 at 5:07pm
Which takes us full circle.  

If you intend to load using .308 Winchester components and .308 Winchester reloading dies, then check the chamber headspace with .308 Winchester gages.  If it fails the .308 Winchester Field gage, better be careful what your doing here, the .308 cases have thinner walls and a ruptured case can result.   By definition, that rifle is no longer safe to shoot with .308 reloads.   If I had a rifle like that, I find out if the chamber headspace is still within 7.62 maximum and only shoot 7.62 NATO ammunition if it is within max. 

Forster makes 7.62 NATO spec headspace gages.  

The good news is that the .308 Winchester and 7.62 NATO specifications for headspace are taken at the same datum on the shoulder, at 0.400 inches diameter.  




Posted By: Goosic
Date Posted: October 16 2020 at 6:40pm
Originally posted by Frameman 1 Frameman 1 wrote:

I fired these rounds yesterday. I used new Hornady 308 cases with CCI 200 primers , Hornady 165 gr, SST bullets with 42 gr. Of IMR 4895 powder. I thought this load would be fine but the signs say otherwise.
Any thoughts? 
Frameman 1. Hodgdon load data shows a starting weight of 41.0grns and a maximum of 43.5grns.
Your 42.0grn charge is right in the middle. It would be advisable to have a competent gunsmith, knowledgeable with the Ishapore Enfield inspect the headspacing.  Brian D i c k at BDLLTD.COM can and will accommodate you and assist with this issue. No sense in playing guessing games from this point forward. Have the headspacing checked before you continue firing the rifle.


Posted By: Frameman 1
Date Posted: October 17 2020 at 2:13am
Thanks for the advice from all our forum friends. I will be contacting Brian for recommendations.

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There are no Americans in Baghdad!!


Posted By: Frameman 1
Date Posted: October 17 2020 at 7:22am
Here is the response I received From Brian @ BDLLTD.com
Hi Roger,

Headsppace specifications for the 2A/2A1 follow.

1.633 Go
1.642 No Go

Those rifles are designed around the 7.62 NATO cartridge and you need to keep pressure down by using 150 grain or lighter projectiles. L2A2 ball uses a 144 grain projectile. I tell folks that if they want a serious 7.62 Lee Enfield, they really need to buy a No.4 which are considerably stronger but still only designed for NATO spec. ball ammo. You're running your pressures up considerably using 168 grain projectiles. Try some 150's and see if they work for you. If you have a local gunsmith with SAAMI gauges, have him check the headspace also. Thanks.

Regards,

Brian  




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There are no Americans in Baghdad!!


Posted By: The Armourer
Date Posted: October 17 2020 at 8:14am
Originally posted by Frameman 1 Frameman 1 wrote:

Here is the response I received From Brian @ BDLLTD.com
Hi Roger,

Headsppace specifications for the 2A/2A1 follow.

1.633 Go
1.642 No Go

Those rifles are designed around the 7.62 NATO cartridge and you need to keep pressure down by using 150 grain or lighter projectiles. L2A2 ball uses a 144 grain projectile. I tell folks that if they want a serious 7.62 Lee Enfield, they really need to buy a No.4 which are considerably stronger but still only designed for NATO spec. ball ammo. You're running your pressures up considerably using 168 grain projectiles. Try some 150's and see if they work for you. If you have a local gunsmith with SAAMI gauges, have him check the headspace also. Thanks.

Regards,

Brian  



Pleased to see both he and I are singing off the same song sheet.

Note he quotes the same headspace and bullet weights as i did several times - even as early as post#3.


Posted By: Goosic
Date Posted: October 17 2020 at 8:48am
Running pressures up considerably usung 168grn projectiles?
Not in the slightest if you follow and adhere to proper reloading procedures. The minimum PSI on this data is listed as 43,800. The calculated conversion to CUP is 37,181. 6000 CUP under that of the working 45,000 CUP of the Enfield rifle. Federal Ammunition uses 41.7grns of IMR4064 and a 168grn SMK BTHP for both the military and in their commercial sales of 308Win. Making this particular 168grn projectile one if the safest loads to use in an Enfield rifle without conflict of interest. The NoGo SAAMI is 1.642" but there is a Field gauge that is 1.638". It would seem to me that as long as headspacing falls between 1.634 and 1.642 the rifle if functional...


Posted By: Honkytonk
Date Posted: October 17 2020 at 9:03am
I'm not sure I understand. I would think pressure is a product of bullet weight and powder load. Heavier bullet? Reduce powder. Net result of producing a round of any weight projectile should be able to achieve a pressure well below maximum... or I completely missing something?


Posted By: The Armourer
Date Posted: October 17 2020 at 9:20am
Originally posted by Honkytonk Honkytonk wrote:

I'm not sure I understand. I would think pressure is a product of bullet weight and powder load. Heavier bullet? Reduce powder. Net result of producing a round of any weight projectile should be able to achieve a pressure well below maximum... or I completely missing something?

That was what I was taught, and I'd also tend to accept the advice & knowledge of a trained armourer and one of the USA's most experienced Enfield 'plumbers'.


Posted By: Goosic
Date Posted: October 17 2020 at 10:47am
God forbid accepting factual load data from one of the leading manufacturers of smokeless propellant like Hodgdon though...


Posted By: Honkytonk
Date Posted: October 17 2020 at 11:18am
Again, I apologize. "... you need to keep pressure down by using 150 grain projectiles or lighter..." and "... You're running your pressures up considerably by using 168 grain projectiles..." I don't understand why that if using a lighter powder charge on the heavier 168 grain projectile and achieving a breech pressure well under the receivers maximum, and unless my elementary understanding of physics is failing me, how can you not load a safe 168 grain round for this rifle?


Posted By: The Armourer
Date Posted: October 17 2020 at 11:32am
Originally posted by Honkytonk Honkytonk wrote:

Again, I apologize. "... you need to keep pressure down by using 150 grain projectiles or lighter..." and "... You're running your pressures up considerably by using 168 grain projectiles..." I don't understand why that if using a lighter powder charge on the heavier 168 grain projectile and achieving a breech pressure well under the receivers maximum, and unless my elementary understanding of physics is failing me, how can you not load a safe 168 grain round for this rifle?

I re-quote my original post (#3)

Heavier bullets accelerate slower than lighter bullets. Slower bullets means less space behind them which means higher pressure, which means faster powder burn which means even more pressure.


Posted By: Honkytonk
Date Posted: October 17 2020 at 11:48am
I understand... BUT... regardless of powder charge and projectile weight, (any combination of the two) with this 7.62x51 barrel on an Enfield receiver, if breech pressure is kept well well below 45,000 cup, regardless of how fast a powder burns, it must be a save round. It all boils down to a combination that respects the maximum breech pressure of the peceiver. 


Posted By: Goosic
Date Posted: October 17 2020 at 11:54am
Originally posted by The Armourer The Armourer wrote:

Originally posted by Honkytonk Honkytonk wrote:

Again, I apologize. "... you need to keep pressure down by using 150 grain projectiles or lighter..." and "... You're running your pressures up considerably by using 168 grain projectiles..." I don't understand why that if using a lighter powder charge on the heavier 168 grain projectile and achieving a breech pressure well under the receivers maximum, and unless my elementary understanding of physics is failing me, how can you not load a safe 168 grain round for this rifle?

I re-quote my original post (#3)

Heavier bullets accelerate slower than lighter bullets. Slower bullets means less space behind them which means higher pressure, which means faster powder burn which means even more pressure.
Not if you are following proper reloading procedures and not attempting to run up to maximum charge weights. Federal Ammunition has load data for a 175gr BTHP SMK using 41.745grn of IMR4064. It has a working PSI of exactly 44,346.7 A PSI to CUP conversion brings that to 37,842.51 CUP, 7100 CUP below the 45,000 working CUP of the Enfield rifle.
I have a tendency to believe Hodgdon and Federal Ammunition over those other two guys you referenced. 


Posted By: Honkytonk
Date Posted: October 17 2020 at 12:07pm
Pressure is pressure. Projectile weight, acceleration, powder charge, primers, brass... If you screw a 7.62x51 barrel on a Enfield receiver, and keep your loads well under say 43,000 cup, and if all the above mentioned components are factored in on this calculation, why would it matter how heavy of a pill you want to push out? "For every action, there is an opposite and equal reaction". Unless this has changed, I truly don't see how projectile weight is the primary factor into producing a safe round.


Posted By: Goosic
Date Posted: October 17 2020 at 12:31pm
Projectile weight is not a factor in producing safe rounds. Producing a safe round consists of following proper reloading procedures.  Trim to length and proper seating depths, minimum powder weight, all factors needed for low to normal working pressures. The projectiles weight is factored into the powder equation and a minimum and maximum amount of powder is given with the disclaimer to never exceed the maximum. You can create an overpressure situation by not trimming the case to length where the edge of the case mouth contacts the throat and can crimp the case fully onto the bullet not letting the case expand during firing to release the bullet. Another excessive pressure situation is when you seat the bullet to just touch the rifling. It doesn't have any run up and excessive pressure is generated to force the bullet into the rifling.


Posted By: The Armourer
Date Posted: October 17 2020 at 1:35pm
Originally posted by Goosic Goosic wrote:

Originally posted by The Armourer The Armourer wrote:

Originally posted by Honkytonk Honkytonk wrote:

Again, I apologize. "... you need to keep pressure down by using 150 grain projectiles or lighter..." and "... You're running your pressures up considerably by using 168 grain projectiles..." I don't understand why that if using a lighter powder charge on the heavier 168 grain projectile and achieving a breech pressure well under the receivers maximum, and unless my elementary understanding of physics is failing me, how can you not load a safe 168 grain round for this rifle?

I re-quote my original post (#3)

Heavier bullets accelerate slower than lighter bullets. Slower bullets means less space behind them which means higher pressure, which means faster powder burn which means even more pressure.
Not if you are following proper reloading procedures and not attempting to run up to maximum charge weights. Federal Ammunition has load data for a 175gr BTHP SMK using 41.745grn of IMR4064. It has a working PSI of exactly 44,346.7 A PSI to CUP conversion brings that to 37,842.51 CUP, 7100 CUP below the 45,000 working CUP of the Enfield rifle.
I have a tendency to believe Hodgdon and Federal Ammunition over those other two guys you referenced. 

How do you know what the working CUP is of the Ishapore Enfields is ?

Dont forget that they changed the steel specification from that specified by the UK and used an 'inferior' grade that mean that the actions warped when tested with both the dry and oiled proof round. After scrapping a large number of rifles they changed to an EN steel which allowed the action to pass the 'dry' proof round, but still failed the 'oiled round' warping the action so that the bolt could not be opened.
The testing specification was altered so that the rifles could be released for use, but it would appear that their strength was very much on the cusp of failing.

I would not want to use anything more than original NATO 144gr rounds (or direct equivalent)

Hogdon & Federal are not aware of which rifles you are using, and probably not even aware of the dubious history of the 2A / 2A1 rifle with regard to pressure and distorted actions.
They are providing you with information to be used on 308 SAAMI firearms.


Posted By: Shamu
Date Posted: October 17 2020 at 2:20pm
Please remember to keep the discussion civil, gentlemen.


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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)


Posted By: Goosic
Date Posted: October 17 2020 at 2:22pm
Originally posted by The Armourer The Armourer wrote:

Originally posted by Goosic Goosic wrote:

Originally posted by The Armourer The Armourer wrote:

Originally posted by Honkytonk Honkytonk wrote:

Again, I apologize. "... you need to keep pressure down by using 150 grain projectiles or lighter..." and "... You're running your pressures up considerably by using 168 grain projectiles..." I don't understand why that if using a lighter powder charge on the heavier 168 grain projectile and achieving a breech pressure well under the receivers maximum, and unless my elementary understanding of physics is failing me, how can you not load a safe 168 grain round for this rifle?

I re-quote my original post (#3)

Heavier bullets accelerate slower than lighter bullets. Slower bullets means less space behind them which means higher pressure, which means faster powder burn which means even more pressure.
Not if you are following proper reloading procedures and not attempting to run up to maximum charge weights. Federal Ammunition has load data for a 175gr BTHP SMK using 41.745grn of IMR4064. It has a working PSI of exactly 44,346.7 A PSI to CUP conversion brings that to 37,842.51 CUP, 7100 CUP below the 45,000 working CUP of the Enfield rifle.
I have a tendency to believe Hodgdon and Federal Ammunition over those other two guys you referenced. 

How do you know what the working CUP is of the Ishapore Enfields is ?

Dont forget that they changed the steel specification from that specified by the UK and used an 'inferior' grade that mean that the actions warped when tested with both the dry and oiled proof round. After scrapping a large number of rifles they changed to an EN steel which allowed the action to pass the 'dry' proof round, but still failed the 'oiled round' warping the action so that the bolt could not be opened.
The testing specification was altered so that the rifles could be released for use, but it would appear that their strength was very much on the cusp of failing.

I would not want to use anything more than original NATO 144gr rounds (or direct equivalent)

Hogdon & Federal are not aware of which rifles you are using, and probably not even aware of the dubious history of the 2A / 2A1 rifle with regard to pressure and distorted actions.
They are providing you with information to be used on 308 SAAMI firearms.
The data for the 168grn M118SB and the 175 M852 that i just referenced are NATO cartridges that are used today and yes
they are providing loading information for 308 service rifles chambered in 7.62x51mm NATO.  What is the 2A/2A1 rifle chambered for?
You keep referencing SAAMI and I can only assume it is because it is not the definitive CIP. 
Norma-Reloading Manual 2004 page 68:
In order to sell products in CIP member countries,  gun and ammunition manufacturers must follow CIP specifications and procedures.  This precaution minimizes potential for accidents that might otherwise result from haphazard production standards. In the US, SAAMI provides very much the same function. BOTH organizations accept each others measurements, pressure standards and procedures. 
The crusher method is time consuming, expensive and unusually sensitive to operator techniques.  For the most part, it also fails to generate results that agree with actual peak chamber pressure. 
 Hodgdon and Federal Ammunition are only aware that their powder and ammunition at sometime will be used in a rifle chambered in 7.62x51mm or commercial 308 and as such offer load information or ammunition that is safe at the time of production.  What you do with it after the fact is none of their concern. The working pressure of the 7.62x51mm NATO chambered Ishapore rifle should have been the same across the board as all the other bolt rifles chambered to accept the 7.62x51mm NATO cartridge in any configuration would be my assumption. Anything less would be unfit for military purposes and sent to a smelter for repurposing.


Posted By: britrifles
Date Posted: October 17 2020 at 5:06pm
This has become a very interesting discussion, and probably one we have had before.  

I respect Brian’s opinion, but here are a few other thoughts.  

I’m not sure why Brian believes that bullets heavier than 150 gr should not be used in the 2A rifle.  Using a powder like H4895, you can load the 168 grain bullet to very mild pressures indeed.  Even reduced loads with a 168 gr bullet to less than 2200 fps is perfectly safe with this specific powder.   Yes, headspace and the throat leade will play a part in what the actual chamber pressure is, it won’t be exactly what is published for .308 Winchester tables as these are for a .308 Win chamber. 

Note that Brian suggested the chamber be checked with SAAMI gages, I’m not aware of any 7.62 NATO SAAMI headspace gages, so I believe he is referring to .308 Win gages.  Here, we are in agreement.   

I do admit that additional caution should be used in loading 7.62 x 51 for No. 1 rifles by using .308 Win load data.  Enfield found the No. 1 rifle unsuitable for conversion to 7.62 due to its weaker action as compared to the No. 4.   But, the beauty of reloading is you have full control of the variables affecting pressure.  Use H4895 and light loads, no more than minimum .308 Win published loads by Hodgdon.  These will have low pressures, well within the .303 British chamber pressures.  Pressure is pressure.  You can get very high chamber pressures with light bullets if you put too much powder in the case. 







 


Posted By: Frameman 1
Date Posted: October 17 2020 at 5:41pm
These headspace gauges are very hard to find.
Anyone rent them?


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There are no Americans in Baghdad!!


Posted By: Goosic
Date Posted: October 17 2020 at 5:45pm
eBay has them. Search 308 headspace gauge. 


Posted By: Frameman 1
Date Posted: October 17 2020 at 5:54pm
I’ll check them out. Thanks 

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There are no Americans in Baghdad!!


Posted By: britrifles
Date Posted: October 17 2020 at 7:21pm
Frameman1, if you are looking to spend the minimum of cash, buy a .308 FIELD gage.  If the bolt does NOT close, you are good to reload using .308 Win load data to MINIMUM charge weights. I strongly suggest you stick with H4895, IMR 4895 or IMR 4064 with 150 or 168 gr bullets.  If you are very confident in your reloading skills, by all means, explore other options of powders and bullets.  

Now that I know that Ishapore 2A rifle chambers were set with fairly long headspace (compared to SAAMI .308 dimensions) I believe this is why you got flattened primers.  The light ring around the circumference of your fired cases should be investigated. If it were me, I would section one of these cases and see how thin the case wall is at that location.  It may well be significant brass stretch from firing a new .308 case in a “long” 7.62 chamber.  




Posted By: Frameman 1
Date Posted: October 17 2020 at 7:42pm
sectioning a case was my goal for tomorrow. I have used 7.62 NATO cases before with no problem. I’m certainly not a pro reloaded but I’m fairly competent.
The field length guage does seem to be the right place to start. It will chamber anything I’ve tried so far so I could pass on the go guage. Like you said “ if it won’t close on the field guage i’m good to go “


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There are no Americans in Baghdad!!


Posted By: The Armourer
Date Posted: October 18 2020 at 12:47am
Originally posted by britrifles britrifles wrote:


Now that I know that Ishapore 2A rifle chambers were set with fairly long headspace (compared to SAAMI .308 dimensions) I believe this is why you got flattened primers.  The light ring around the circumference of your fired cases should be investigated. If it were me, I would section one of these cases and see how thin the case wall is at that location.  It may well be significant brass stretch from firing a new .308 case in a “long” 7.62 chamber.  



13thou difference.








Posted By: britrifles
Date Posted: October 18 2020 at 4:56am
Yes, if this chamber is at or close to 7.62 MAX, it will not be safe to shoot reloads with .308 cases.  Not even with minimum charges.  Even 7.62 cases will stretch significantly causing case wall thinning, and case life will be very short if headspace is close to 7.62 MAX.  If he’s lucky, the chamber may be closer to the 7.62 MIN dimension which is shorter than the .308 FIELD:  

    Ishapore 7.62 MIN 1.633 is .005 shorter than .308 FIELD 1.638

    Ishapore 7.62 MAX 1.642 is .004 longer  than .308 FIELD 1.638 

There is overlap on these dimensions and the chamber may well be under .308 FIELD and safe to reload with .308 Win cases.  

We are all just speculating, the headspace needs to be checked.  If it fails the .308 FIELD gage, then the only hope for continued use is to check it with a 7.62 MAX gage and if it passes, reload with 7.62 NATO cases only.  I would not recommend shooting a lot of 7.62 NATO ammunition even if it’s less than 7.62 MAX.

New 7.62 X51 NATO cases are available, currently on sale at Midway USA.  7.62 MAX headspace gage available from Brownells for $32.00.  







Posted By: Frameman 1
Date Posted: October 18 2020 at 5:48am
I pulled the trigger for the Max 7.62 gauge. I’ll update when I have it.



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There are no Americans in Baghdad!!


Posted By: britrifles
Date Posted: October 18 2020 at 6:26am
One other thing, you will find some variability in .308 FIELD gage dimensions.  I got my set from Manson Precision, the Field gage is 1.640, 0.010 longer than the .308 GO gage and only .002 shorter than the Ishapore MAX chamber length.  






Posted By: Frameman 1
Date Posted: October 18 2020 at 6:54am
That info illustrates that the 7.62 chamber is considerably longer than the .308.
I’m considering doing a chamber casting to help clarify the issue.


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There are no Americans in Baghdad!!


Posted By: The Armourer
Date Posted: October 18 2020 at 8:00am
Originally posted by Frameman 1 Frameman 1 wrote:

That info illustrates that the 7.62 chamber is considerably longer than the .308.
I’m considering doing a chamber casting to help clarify the issue.

That should be an interesting exercise.
Look forward to seeing some conclusions.


Posted By: Goosic
Date Posted: October 18 2020 at 8:12am
Originally posted by Frameman 1 Frameman 1 wrote:

I pulled the trigger for the Max 7.62 gauge. I’ll update when I have it.

MIXING AND MATCHING BRANDS OF HEADSPACE GAUGES - Don't do it!! That's the short answer, here's why. It boils down to tolerance stacking. Each Headspace Gauge manufacturer works within a range specified by SAAMI. Manufacturer "A" may work at the high end of the range while Manufacturer "B's" gauges are in the middle of the tolerance range. Mixing the two could give an inaccurate reading. By sticking with one brand within a particular caliber, you will eliminate a variable. If you have a Forster, .308 GO gauge, get a Forster, .308 NO GO. Use Clymer with Clymer and Manson Precision with Manson Precision, etc. You can use any brand of headspace gauge with any other brand of chambering reamer. e.g. Forster Headspace Gauges with Clymer Reamers, Manson Precision Gauges with JGS Reamers, etc.


Posted By: Goosic
Date Posted: October 18 2020 at 8:17am
Originally posted by Frameman 1 Frameman 1 wrote:

That info illustrates that the 7.62 chamber is considerably longer than the .308.
I’m considering doing a chamber casting to help clarify the issue.
DiamondKBrass.com sells certified once fired 7.62x51mm NATO brass and brand new and primed Lake City 7.62x51mm NATO brass. The prices are amazing for the once fired stuff.


Posted By: The Armourer
Date Posted: October 18 2020 at 9:32am
Originally posted by Goosic Goosic wrote:

Originally posted by Frameman 1 Frameman 1 wrote:

That info illustrates that the 7.62 chamber is considerably longer than the .308.
I’m considering doing a chamber casting to help clarify the issue.
DiamondKBrass.com sells certified once fired 7.62x51mm NATO brass and brand new and primed Lake City 7.62x51mm NATO brass. The prices are amazing for the once fired stuff.

Good advice.
As shown by manufacturers making 'brass' to SAAMI specifications - most of them work to the 'bottom half' of the tolerance limits.
Rim thickness on 303 is specified as 0.064" + zero, - 10 thou (0.064 max and 0.054 min)

The majority of Win, Rem etc is below 0.058 (but batches vary) whilst the likes of PPU are up around 0.060" - o.o62"

Comparison of unfired Win 303 and a PPU 303 - case wall thickness and secondly same manufacturers rim thickness













Posted By: Honkytonk
Date Posted: October 18 2020 at 10:21am
I am sold on PPU brass for my .303's. I've reloaded each of the first 100 I bought at least four times and they still look great. Got a brand new bag of 100 I haven't even touched yet. Never had that kind of longevity from Winchester or Remington.


Posted By: Shamu
Date Posted: October 18 2020 at 10:43am
Respectfully to all involved.
You can not compare rimmed to rimless brass.
The working of the brass during firing is so different such comparisons are misleading at best.
Compare apples to apples & oranges to oranges for more meaningful results is my suggestion.


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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)


Posted By: Honkytonk
Date Posted: October 18 2020 at 11:01am
Sage advise...


Posted By: Frameman 1
Date Posted: October 18 2020 at 11:50am
I’ll risk a bit of flaming with this measurement. Since I don’t yet have a headspace gauge I decided to check the head clearance. I used a 7.62 NATO once fired casing and removed the primer without resizing of any kind. I took a case length measurement then partially reinserted the primer , closed the bolt on this case and removed and measured again for length. I came up with 0.005” difference.
This sounds to be a pretty small clearance gap.
Anyone have any thoughts on this?


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There are no Americans in Baghdad!!


Posted By: britrifles
Date Posted: October 18 2020 at 12:49pm
You should use a new 7.62 case.    The fired case has already been elongated to fit the chamber, minus the brass relaxation after firing. 

I’m not a fan of buying once fired 7.62 cases, they may have been fired in long 7.62 NATO chambers and already have thinned case walls from stretching.  Midway has a very good deal in new NAMMO 7.62x51 cases, $30 for 100 cases. 

I don’t think you will get an accurate headspace measurement from a chamber cast.  




Posted By: The Armourer
Date Posted: October 18 2020 at 12:53pm
Originally posted by Frameman 1 Frameman 1 wrote:

I’ll risk a bit of flaming with this measurement. Since I don’t yet have a headspace gauge I decided to check the head clearance. I used a 7.62 NATO once fired casing and removed the primer without resizing of any kind. I took a case length measurement then partially reinserted the primer , closed the bolt on this case and removed and measured again for length. I came up with 0.005” difference.
This sounds to be a pretty small clearance gap.
Anyone have any thoughts on this?

I could be misunderstanding, but what you look to have done is 'replicated' measuring the rimmed case headspace. What you have done is measure the gap between the rim and the front of the bolt head by measuring the distence the primer is NOT pushed in.

On a non-rimmed case the headspace is part way down the neck of the chamber (somewhere between the 2 shoulders) I don't think you can measure that using a primer - you need to measure the diameter of the chamber where an unfired case (not stretched) touches the circumference of the neck at the correct point,


Posted By: Frameman 1
Date Posted: October 18 2020 at 12:57pm
no not exactly.
What I am measuring is the gap behind the she!! case a the bolt face. I believe this is referred to as bolt head clearance. .


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There are no Americans in Baghdad!!


Posted By: The Armourer
Date Posted: October 18 2020 at 1:15pm
Originally posted by Frameman 1 Frameman 1 wrote:

no not exactly.
What I am measuring is the gap behind the she!! case a the bolt face. I believe this is referred to as bolt head clearance. .

Correct, which is part of the function of headspace on a rimmed cartridge, but is meaningless for a non-rimmed cartridge.


Posted By: Frameman 1
Date Posted: October 18 2020 at 1:22pm
Using a fire formed 7.62 case essentially acts as a headspace gauge the protruding primer pushes the case against the chamber walls at the case shoulder. As the bolt is cammed forward into place the primer is forced further into the case.
The remaining primer protrusion is the head clearance gap.
This gap should be somewhat relevant.


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There are no Americans in Baghdad!!


Posted By: Goosic
Date Posted: October 18 2020 at 2:14pm
Originally posted by britrifles britrifles wrote:

You should use a new 7.62 case.    The fired case has already been elongated to fit the chamber, minus the brass relaxation after firing. 

I’m not a fan of buying once fired 7.62 cases, they may have been fired in long 7.62 NATO chambers and already have thinned case walls from stretching.  Midway has a very good deal in new NAMMO 7.62x51 cases, $30 for 100 cases. 

I don’t think you will get an accurate headspace measurement from a chamber cast.  


I do not see an immediate issue if the certified once fired 7.62x51mm NATO brass is full length resized, prepped accordingly, and then neck sized after firing for that particular rifle.


Posted By: Frameman 1
Date Posted: October 18 2020 at 2:21pm
I agree with britrifles that a chamber cast would be very difficult to determine headspace but would serve to expose throat erosion, and bullet jump.Besides I’m bored and want to try something new to me😎

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There are no Americans in Baghdad!!


Posted By: Frameman 1
Date Posted: October 18 2020 at 2:28pm
Using a new case as opposed to a fire formed case to check head gap clearance would be an interesting comparison.



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There are no Americans in Baghdad!!


Posted By: The Armourer
Date Posted: October 18 2020 at 2:49pm
Originally posted by Frameman 1 Frameman 1 wrote:

Using a fire formed 7.62 case essentially acts as a headspace gauge the protruding primer pushes the case against the chamber walls at the case shoulder. As the bolt is cammed forward into place the primer is forced further into the case.
The remaining primer protrusion is the head clearance gap.
This gap should be somewhat relevant.

Sorry, I just dont see it.

Yes your 'primer' is showing the head clearence, but, it is not showing headspace which is the measurement you are trying to take.
So your 'primer test' shows a a 0.005" head clearence - how do you translate that into a headspace reading  - where exactly do you measure from on the case taper back to the primer to get the headspace ?

I'm not sure how else to explain it but, the head space is the measurement taken at a specific diameter on the slope of the shoulder. Forcing a fired case into the chamber is showing (doing) nothing to actually identify :
a) The point where the measurement is taken
b) The dimension at that point

The case will be forced into the chamber by the camming action of the bolt, if it has expanded it will be forced into the chamber irrespective of where the shoulders were, or are, after firing.

On a Rimless round You can only measure headspace by using a headspace gauge.


Posted By: Frameman 1
Date Posted: October 18 2020 at 4:18pm
I wasn’t trying to find headspace by measuring the head clearance gap. I understand they are two different measurements. I was simply trying to find the clearance gap to see if the two measurements have any bearing on each other. I have the “coin” style headspace gauge for my Mosin Nagant rifles that measures from the breech face of the chamber to the bolt face. Which is a fixed point of the chamber. The distance between the shoulder datum to the bolt face is also a fixed point for rimless rounds. 
I am simply substituting the fire formed case with protruding primer to measure the same distance as an legit gauge. 
I realize this method isn’t as consistent or as repeatable as using a real gauge but might be an approximation that might be useful. 


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There are no Americans in Baghdad!!


Posted By: britrifles
Date Posted: October 18 2020 at 6:24pm
All cartridge cases will lengthen upon firing unless the rifle chamber headspace and cartridge headspace is practically the same.  The brass cannot hold the pressure without restraint from the thick steel chamber.  The brass plastically deforms to fill the chamber upon firing.  When the chamber pressure drops, the case stresses will relax and the case will slightly retract based on the brass stress/strain relationship.
  
What you are measuring with the primer in a fired case is the amount the case relaxes after firing (plus the very small amount the bolt compresses under the thrust loads).  What you want to measure is “head clearance”, the distance between the bolt face and head of the case with the case fully forward in the chamber.  To so this, you must use a new unfired case.  I’d expect it will be close to .010 in your chamber.  

The Armourer is correct, that will not give you the actual headspace dimension in your rifles chamber, but will give you an idea how much the brass is straining under the first firing.  Excessive permanent strain is what causes case ruptures.  In a Long chamber, the damage is done on first firing, full length resizing cannot repair this damage. 







Posted By: Frameman 1
Date Posted: October 18 2020 at 6:33pm
I see what you gentlemen are saying. I will measure it with an unfired case.
Very interesting!


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There are no Americans in Baghdad!!


Posted By: britrifles
Date Posted: October 19 2020 at 7:26pm
I highly recommend this Hornady case headspace gauge for those that reload. $42.00 here in the US available at most places that sell reloading supplies.  Calipers not included.

Comes with 5 bushings corresponding to the diameter of the datum reference on the case shoulder to measure case headspace (e.g. 0.400 inches for the .308/7.62 NATO cartridge).  For rim cartridges like the .303, it is very useful to set up your FL sizing die to minimize how much you set the shoulder back by first measuring a fired case, then adjust the die to shorten the case head to shoulder length by .002 to .004 inches.  A bit of trial and error when adjusting the die position in the press, but will significantly increase the life of the brass.  The chamber lengths on my No. 4 .303 rifles vary considerably, perhaps by as much a 0.05 inches, so I sort and resize brass for each rifle separately. 

I use this gauge to set the FL resizing dies on all my bolt action centerfire rifles.  Auto loading rifles should have dies set to fully FL size the case to standard cartridge dimensions to ensure reliable feeding and minimize chances of a slamfire or out of battery discharge.  For this, I use the simple cylindrical case length gauge from LE Wilson to set up the die.  







Posted By: Shamu
Date Posted: October 20 2020 at 7:24am
I also have, use & recommend these.
They're especially good on rimless cases because the insert is sized to stop at the "datum point" on the case shoulder so you know the measurements are correct.
I would suggest using them with a digital caliper, not a dial though.
There is an adapter & a gauge to zero for its much easier with digital's push button zero.
I don't know about the Hornady version, I bought mine before they bought the makers out. Mine also came with another adapter & gauge set for bullet seating to ogive!
Very handy toy.


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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)


Posted By: Goosic
Date Posted: October 20 2020 at 11:02am
How does it help to improve accuracy?


Posted By: britrifles
Date Posted: October 20 2020 at 11:32am
I don’t think these improve accuracy, they will make it easier to ensure you don’t excessively size the brass for the chamber of your rifle and thereby extend brass life.  For the .303, I believe that neck sizing as long as possible (until you feel resistance to locking the bolt) then minimal (partial) full length size just enough to push the shoulder back .002 to .004 inches will significantly extend the life of the brass.  With this approach, I’ve gotten about 50 reload cycles on my .303 brass (partial length resize about every 10 to 12 neck sizing cycles). 

The Wilson case gages are good to ensure reliable feeding in self loading rifles, I use them to check the first few cases coming out of the full length sizing dies.  Failure of the bolt to fully lock can ruin your day.  I like to be sure I don’t get a chambering problem during the rapid fire stages of the match.  



Posted By: Goosic
Date Posted: October 20 2020 at 12:29pm
Is it a tool that would benefit me?


Posted By: britrifles
Date Posted: October 20 2020 at 1:41pm
I think so Goosic.  I find it very useful.  And not expensive either.


Posted By: Goosic
Date Posted: October 20 2020 at 1:46pm
Natchez has one for $33.00.
I bought it. Expect me to ask you a bunch of questions now when I start to use it. 


Posted By: britrifles
Date Posted: October 20 2020 at 1:57pm
No problem Smile


Posted By: The Armourer
Date Posted: October 20 2020 at 3:50pm
Originally posted by <div><br></div><div>The Wilson case gages are good to ensure reliable feeding in self loading rifles,  </div><div><br></div>[/QUOTE

The Wilson case gages are good to ensure reliable feeding in self loading rifles,  

[/QUOTE wrote:



They are pretty good for 'batching' rounds with similar rim thickness  to give you consistent shooting.

They are pretty good for 'batching' rounds with similar rim thickness  to give you consistent shooting.

Also clearly show the difference in rim thickness between PPU and SAAMI cases. (PPU top)






Posted By: Goosic
Date Posted: October 20 2020 at 4:14pm
My 308 brass is mainly Lake City, followed by Lapua, then Norma. 
I would like to start separating and using only the Lake City for my Remington, the Lapua for the fully dressed No4Mk1/2 and the Norma for everything else. 


Posted By: britrifles
Date Posted: October 20 2020 at 7:08pm
Originally posted by The Armourer The Armourer wrote:

Originally posted by <div><br></div><div>The Wilson case gages are good to ensure reliable feeding in self loading rifles,  </div><div><br></div></td></tr></table>
<div><br></div><div>They are pretty good for 'batching' rounds with similar rim thickness  to give you consistent shooting.</div><div><br></div><div>Also clearly show the difference in rim thickness between PPU and SAAMI cases. (PPU top)</div><div><br></div><div><img src=uploads/5736/Rim_Thickness_gauge.jpg height=614 width=355 border=0 /></div><div><br></div><div><br></div><div><br></div>[/QUOTE

The Wilson case gages are good to ensure reliable feeding in self loading rifles,  


They are pretty good for 'batching' rounds with similar rim thickness  to give you consistent shooting.

Also clearly show the difference in rim thickness between PPU and SAAMI cases. (PPU top)




[/QUOTE wrote:


The recess for the rim in the Wilson gage is much deeper than the rim thickness.  What you are seeing on the RP “SAMMI” case sitting below flush with the gage is not because of rim thickness, it is the case dimension from the head to the shoulder.  If you invert the case and insert it, you will see that the forward face of the rim sits well below the surface of the gage. 



The recess for the rim in the Wilson gage is much deeper than the rim thickness.  What you are seeing on the RP “SAMMI” case sitting below flush with the gage is not because of rim thickness, it is the case dimension from the head to the shoulder.  If you invert the case and insert it, you will see that the forward face of the rim sits well below the surface of the gage. 




Posted By: Frameman 1
Date Posted: October 22 2020 at 3:48pm
Well today I received my 7.62 NATO Field headspace gauge and the Hornady case length insert (.400) 308 Caliber. 
I removed the firing pins and extractors from both my Ishapore rifles. Neither bolt would close with gentle pressure. They had about 3/16” to fully closed. I also used a once fired PPU 7.62x51 case and inserted it into the chamber of the rifle from which it was fired. The bolt closed with no resistance and when fully closed it had zero fore or aft movement. I’m happy with these results. Now I can start to build custom Ammo for each individual rifle. I will also be following a much more conservative powder charge formula.


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There are no Americans in Baghdad!!


Posted By: britrifles
Date Posted: October 22 2020 at 7:44pm
Good news.  

Just continue to shoot and neck size the brass until you feel some resistance in closing the bolt.  When that happens, use your Hornady case length measuring tool to measure the length of the case (shoulder to case head) and adjust the full length die to shorten the case by .002 to .004 inches.  Check the sized case in the rifle chamber to be sure the bolt closes with no resistance, then continue again with neck sizing only.  You should get 30 or more reload cycles out of your brass.  You might have to separate the brass between the two rifles if the case headspace lengths are different by more than .005 or so. 

I suspect you will not see flattened primers with the neck sized cases with reasonable charge weights.  Load to .308 minimums.  You can go even lower than .308 minimums with H4895.  No reason to push these rifles to near max velocities.  

Are the PPU cases Identified as 7.62 NATO or as .308 Winchester?




Posted By: Frameman 1
Date Posted: October 22 2020 at 7:47pm
The PPU are 7.62 NATO 

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There are no Americans in Baghdad!!


Posted By: shjoe
Date Posted: October 23 2020 at 10:18am
most of my reloading is with fireformed cases segregated to each rifle. i then neck size only using cast bullets and moderate velocities @1700fps. i get good case life and accuracy with lower pressures when compared with loading jacketed rds. best regards, john


Posted By: Frameman 1
Date Posted: October 23 2020 at 12:09pm
I’ve not tried cast bullets. Sounds interesting.

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There are no Americans in Baghdad!!



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