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3 Ishapores all the same

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Merlin54 View Drop Down
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    Posted: January 20 2020 at 3:17pm
I routinely load 308 based cartridges.  The head space measures 1.625 or thereabouts.  I know very little about the Ishapore except years ago they were super cheap so I bought 3 and one of which is still in cosomoline.  I decided to fire two of them after cleaning them up and replacing the extractor springs which apparently made closing the bolt on a round very difficult.  They both fired and to the point of aim. However...  The shoulder on the brass moved from 1.625 to right at 1.640.  This is extreme!  
  I have in hand commercial 308 win and 7.62x51 nato ammunition.  The shoulders on both are 1.625.  The fired commercial 308 silver tip had the neck split as well as the shoulder blown out to 1.640.  The 7.62x51 necks were not split but the shoulders were also blown to 1.640.  Dirt, sand, OK but why the devil make the rifles with these enormous chambers?

My question is this. Can I fire-form 308 brass using a mild 308 starting load to blow out the shoulder and just set the shoulder back 0.002 to 1.380 to reload for these rifles?
Of course the brass may be too thin after stretching to do this.  The only reason I ask is that I have a wildcat cartridge in an Encore rifle that was made from a 30-30 win.  It was necked down to 6.5 and then the shoulder blown out to add case capacity.  
I would be interested in any opinions or answers to the question --can one reload for the Ishapore.   I have most of the military rifles from WW1 and WW2 except for the NO.1 MK3 so these Ishapores hold a certain interest  for me.
Thanks
Ralph Key
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Bear43 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bear43 Quote  Post ReplyReply Direct Link To This Post Posted: January 21 2020 at 7:50am
The Lee-Enfield rifle is known for its generous chambers. Why? Think mud of the trenches. They are set up to operate in some very severe conditions. People reload for them all the time but that isn't my area of expertise so I'll let one of the reloaders answer the rest.
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britrifles View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Posted: January 21 2020 at 8:08am
My No. 4 Mk2 DCRA conversion to 7.62 done by Long Branch has a chamber that does not close on the .308 No-GO gage; it does close on the GO gage at 1.630.  1.640 would be the .308 field gage.  Depending on how you are measuring the case headspace after firing, you should be OK to fireform and then resize as you have suggested. 
 
A previous post talked about the many different standards used on 7.62 chambered rifles, so no telling what Ishapore did for the 7.62 No. 1 rifles. 
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BJ72 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BJ72 Quote  Post ReplyReply Direct Link To This Post Posted: January 21 2020 at 3:07pm
If your measurements are correct, you are still within spec for a 7.62 NATO chambered rifle. Like Bear said, these rifles are set up for use in harsh conditions. They were not set up as target rifles with tight tolerances. The longer sloppy chamber fit on a lot of NATO chambered rifles is why it's best to use military brass which has thicker side walls, especially near the case head. Once fire formed on the initial firing, resize just enough to chamber freely back in that particular rifle. If you want to use commercial 308 brass, and you are worried about stretching the case during the initial firing you can use the same method a lot of wildcat cartridge shooter use to fire form brass to fit a particular chamber.

To avoid stretching the case head at the initial firing and extend case life, neck new 308 Win cases up to say .338" or .358” caliber and then resize in a full length 308 die so as the case is sized just enough to chamber with a bit of feel as the bolt closes. This will leave a very small step at the shoulder – neck junction which the cartridge will headspace off until it is fire formed at the initial firing. Then resize fired cases to suit your chamber. In your case, don’t set the shoulder back any further then say 1.6380”. This method ensures the brass is worked (stretched) around the shoulder area and not at the case head.

If it was me, I'd just use NATO spec brass and size to suit after initial firing.


As far as NATO specs go, I got this direct from the Forster wed site a while back. Their max for 7.62 NATO is 1.6455".

Forster Products

NATO CHAMBER HEADSPACE GAGES (GAUGES)


NATO Chamber Headspace Gages Instructions. There can be great differences between the chambers of military rifles based on the type of action (FN, Garand, Ishapur, etc) and also based on the amount of use the rifle has seen. Forster Products NATO Minimum rifle chamber gages check to see that the rifle will accept the longest (headspace dimension) NATO ammunition cases that are currently manufactured. The Forster NATO Maximum rifle chamber gage checks to see that the rifle does not have excessive headspace, which could lead to dangerous pressure problems.

Similarly, the 5.56 NATO caliber requires a slightly longer headspace than the commercial .223 caliber, which are commonly thought to be identical. For that reason, Forster Products is also offering 5.56 NATO Headspace Gages. For any gunsmith or armourer working with military firearms in these two calibers, these NATO Headspace Gages can make a huge difference in both performance and safety.

Two gages (Minimum Headspace and Maximum Headspace) are available per caliber. 


 

Order No.

Description

HG556NATOMin
(minimum chamber)

5.56 NATO Headspace Gage - length is
1.4636" plus .0003" minus zero

HG556NATOMax
(maximum chamber)

5.56 NATO Headspace Gage - length is
1.4736" plus Zero minus .0003"

HG762NATOMin
(minimum chamber)

7.62 NATO Headspace Gage - length is
1.6355" plus .0003" minus zero

HG762NATOMax
(maximum chamber)

7.62 NATO Headspace Gage - length is
1.6455" plus Zero minus .0003"

My idea of gun control is hitting what I aim at and nothing else.
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The Armourer View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote The Armourer Quote  Post ReplyReply Direct Link To This Post Posted: January 22 2020 at 1:51am
Remember that a 308 is not a 7.62.
The 7.62 has a 13 thou (0.013") longer headspace than the 308 Win

This may be of interest :

A lecture given by Peter Laidler (The UK's most senior Armourer)

Anyone for 7.62mm CHS?
Posted By: Peter Laidler
Date: Tues 6 May 2008 11:36 am
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.

The fact remains that there are MANY gauges for all manner of 7.62mm rifles and machine guns ranging from the little bolt action L8’s right through to the L- whatever it is ferocious mini gun. And there are equally MANY for different lines of repair and functions, ranging from 1.622” to 1.648”.

That just about covers the 7.62mm versions. The question of calibrating your gauges is one that needs to be looked into by ‘some friends’ on both sides of the pond. I can see already that this is about to open up a whole new can of worms...... But just hang on in there....................




He subsequently spoke with the Indian Army Liasion officer at Warboys who found out the Ishapore headspace.

Again from Peter :

Don't say I don't try hard for you. The CHS for an Ishapore 2A1 is (They call it LOW) is GO 1.633" and HIGH or NO-GO is 1.642.

Now the observant of you will immediately see that this just about/almost/nearly/neatly inside the 7.62mm L1A1 limits of 1.6325 and 1.643". It's a bit higher that I would have expected from a bolt action rifle BUT, it is still the generally accepted .010" between go and no-go.

I don't know about Indian production at all. BUT, due to the fact that they made some of the rifles using bog standard old No1 bodies (which defeats the myth that they were made from higher quality steel - they weren't), it stands to reason that they'd use bog standard bolt heads and bolts too. If they used different size bolts and heads for the different calibres, then presumably, like any sensible person, they'd mark them, like we did with the 7.92mm/.303/7.62mm Bren bolts otherwise there would/could be a catastrophic failure.

On that basis, the chamber would be bored to a depth in relation to the breeching up geometry which ensured that when the barrel was breeched up, the distance from the datum line in the chamber to the face of the bolt head was between 1.633 and 1.642"

As for exactly which point in the neck that the Indian Engineers take their CHS datum from, well I can't answer due to the fact that I cannot calibrate an RFI set of CHS gauges against our own specification. BUT, at the risk of being wrong - as I was when I ventured to suggest originally that the CHS would be the same as the L39/42/96 etc etc, I'd say that it was the same datum as standard NATO.
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450 Fuller View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 450 Fuller Quote  Post ReplyReply Direct Link To This Post Posted: June 08 2022 at 8:45am
Being a new member, but an ancient old handloader for decades-this is valuable
data as to tolerances and strengths.
I tend to stay on the moderate line as to pressures when reloading for the SMLE in 7.62.

Some of my reloading effort extends to the 348 WCF Ackley Improved and the 375
Holland & Holland.
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