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Reloading Info for 174 gr Bullet

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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: May 13 2020 at 9:05am
 We kinda drifted from the original topic, but here is a photo of an unfired (on left) and a cracked (on right) DI 1943 Mk 7 case that is sectioned.  The case web cracks occur at 0.32 inches above the Bottom surface of the head.  The web thickness at this location on a new case measures 0.035 inches thick.  

The unfired case weighed 168.4 grains, 2.207 inches long, 0.452 inch diameter just above the rim and a 0.064 thick rim.  


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Zed Quote  Post ReplyReply Direct Link To This Post Posted: May 13 2020 at 10:22am
Britrifles, regarding your question on how a radial expansion can cause a split on the circumference.
Is it possible that the case is working in two directions in this area when fired? 

If the chamber is a bit large in the diameter. (which seems quite common in LE's) As the powder chamber area of case expands outwards to grip the chamber wall, the rim end of the case will move rearward to take up any slack in the head space as we know; but the case in front of the reinforced area around the primer will also expand outwards. The ring appears at the join of the stronger rim area and the powder chamber case thickness. Could this explain the difference in number of reloads in rifles that have known good headspace?

On one of my rifles I get the impression that the cases do blow outwards slightly at this area. Cases from this rifle do not chamber in the other's.
I'll have to measure them after the next range trip; all my brass is resized and waiting for the range to open at the moment.

With regard to the original poster asking about the "O"ring method. I suggest he reads Peter Laidler's opinion on that. You certainly don't need "O"rings if the rifle headspace is good; and if the headspace is out of specification with the largest bolt head; then it's probably the receiver thats worn out. But the tool for checking that is probably impossible to find!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Posted: May 13 2020 at 12:21pm
Zed, 

There is certainly bi-axial stress in the case from the internal pressure.  When the case yields in the radial direction (which occurs first since the hoop stress On the case is 2x the axial stress), it will first pull the head forward and take up any head clearance.  But as pressure builds, and radial expansion is restrained by the chamber,  the case head will then get blown back firm against the bolt.  It is this plastic axial overload strain on the brass that causes the thinning (“necking” is the technical term).  You will see in the photo above that it occurs above the juncture of the web and solid head area, not at it.  The exact location of the necking will likely vary somewhat depending on specific case dimensions.  

This is not a fatigue crack, the thinning (necking) is an overload rupture failure from exceeding the materials yield (and ultimate) strength.  

In reality, it is probably more complex than this involving localized bending stresses at the juncture of the case head, as you pointed out, the chamber diameter is considerably larger than the case and the case head restrains radial expansion at this point. The length of the case that has not firmly gripped the chamber also plays a role, so another effect of chamber geometry.  

I’m no expert, not trying to insinuate I am, just applying some basic engineering principles to the problem.  

How much of this is also influenced by the rear locking lug design would take some calculation (how much the bolt compresses under load) but that’s just more than we need to know.  Reload until you see the white line and then toss the case.  If your fortunate to have some spare bolt heads, try to minimize the head clearance based on the brass you are using.  But, I would be very careful in reducing headspace below minimum (0.064), this could result in not being able to lock the bolt on a thick rim cartridge, that would be potentially dangerous.  




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Post Options Post Options   Thanks (0) Thanks(0)   Quote Zed Quote  Post ReplyReply Direct Link To This Post Posted: May 13 2020 at 1:08pm
I tossed a lot of Remington cases when seeing the ring appear. After having one or two heads seperate, you learn quickly to spot the fault line.
I must say that I'm much happier with the PPU cases.
The last bag of Remington that I bought appeared thinner than the older ones; especially around the neck area. I have not loaded any of this bag; having just stored them since moving on to the PPU's. I'll try and measure both old and new Remington cases and compare.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: May 13 2020 at 4:00pm
I've never had a case "let go" there!
I have had cases separate, but its further forward?
Several rifles, multiple brass brands & decades of shooting?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Posted: May 13 2020 at 4:06pm
I had 200 RP cases I bought about 20 years ago.  I’ve not used them much, I reloaded these for my Dad’s No. 4(T), maybe 8 times now, no issues yet.  The barrel on this rifle is a Long Branch six groove RH twist that hadn’t had many rounds thru it.  

RP cases had not available for a while so when I saw them listed again recently I bought a few hundred, haven’t looked at them yet.  

I weighed a number of PPU cases, average was 170 gr. IIRC.  Comparable to the Mk 7 cases I have.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote paddyofurniture Quote  Post ReplyReply Direct Link To This Post Posted: May 13 2020 at 4:10pm
Do nickel plated cases last or do they crack and die?
Always looking for military manuals, Dodge M37 items,books on Berlin Germany, old atlases ( before 1946) , military maps of Scotland. English and Canadian gun parts.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: May 13 2020 at 4:12pm
In my experience they are terrible. I don't know why. I only use them as "fire & forget" ammo. now to be fair these are all Remington nickle cases, others may be fine.
I used to be a big fan of Remington Brass. No longer unfortunately Prvi Partizan has them hammered on both quality & price.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote MJ11 Quote  Post ReplyReply Direct Link To This Post Posted: May 13 2020 at 6:47pm
Well this has been an interesting post.

Without pulling my log book I can't remember getting 3 reloads out Remington brass. They were normally dis guarded after two loads after feeling the inside of the case head and web area with a small bent probe. You could locate the failure line by feel and then you would recognize the area out side from then on and the dis guard number rocketed up. Winchester was equally bad. Lapua was good but I have only shot them four times so I can't put a real limit there.

Tonight reading this I pulled out my Brown & Sharp calipers calipers I got when I graduate the Small Arms course at Armament Command school in 1966. Locked up from lack of use. Thirty minutes later after a careful cleaning years over due I got a .059" rim on my much vaunted Greek HXP 1976 ball.

As an aside I once took my 7.62X51 Enfield to a match with once fired LC Match brass with the little band of knurling 1/4" above the extractor  grove. Second shot in the match at 200Y the case head came off right there leaving the LCM case in the chamber. Both rounds had been in the 9 ring side by side with iron sights. But I was out and that ghost played he!! on me for a long time. by the time I cleared the stuck case it was time to pack up and go home. I stayed and put ten ten rounds of some Spanish .308 cases that had been through my HK 91 loaded for 500 Y + eight times. I had five bulls and a few nines and eights. The HK is brutal on brass with the gas serrations and violent ejection cycle. Ca-rumba I miss that rifle. But it worked well in my #4 7.62 Enfield. It's crap shoot out there boys.

I have some PPU 303 coming for the three new to me rifles this week. I will be interested in the results run side by side with new 174g HXP and 174g PPU and then the reloading comparison.

While I'm not an expert on anything the results should be interesting to some degree. 

Another note maybe ten years ago I bought 400 PPU bullets called .311" 174g Match. They were anything but . The weight was all over the map from 167g to 175g and I never had two shots fall within 1.5 MOA of the last when we still had the 200Y line open at the same time as the 300Y and 500Y steel plates. I was careful with assembling that I gave up and just went with the average from then on and worked on my job. A hit is a hit restored my faith in the #4.

I hope this post grows because I will watch it and learn from all the experts.

Cheers

200Y

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Post Options Post Options   Thanks (0) Thanks(0)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Posted: May 14 2020 at 4:51am
Interesting MJ.  I may have been lucky with the small batch of RP cases I have.  I don’t think I’ve had to FL size them yet.  They have so far held up well in Dad’s No. 4(T).  Next time I’m up in Ontario, I’m going to check the headspace on this rifle.  It was done by a very competent DCRA Armourer in Ottawa back in the ‘60’s, so I expect it is right at minimum.  

I measured the rim thickness on my RP cases at 0.059 to 0.060.  I don’t expect they will last as long as my Canadian military cases.  


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Post Options Post Options   Thanks (0) Thanks(0)   Quote 303Guy Quote  Post ReplyReply Direct Link To This Post Posted: July 08 2020 at 2:22am
If I may make a comment, realizing the thread is a few months old but head separation and case life in the Brit is a function of smoothness of the chamber and dryness of the loaded case.  Lube the loaded cases and they will last forever.  Dry them and expect three to five loadings.  

Lubing means rolling them lightly on the lube pad.  This does not prevent case wall grip but does limit the grip, allowing the case to elongate over the full body length while the neck itself does not move.  This practice prevents case elongation and doughnut creep.  It does not increase bolt face thrust as there is not enough lube to float the case.  There is still a degree of bolt face thrust reduction though, about as much as a dry case provides on first firing.

The fact that the case wall is elongating and thinning means the case is not carrying as much thrust load since the case is actually progressively failing on each firing with progressively less thrust reduction, as little as it was to start with.  The maximum thrust a case can carry is the stress area of the case wall, which once it reaches yield point drops off because the material has failed, i.e. undergone plastic deformation.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Posted: July 08 2020 at 7:22am
I’ve never lubed the cases, and I typically get 50 reload cycles on military brass.  I haven’t reloaded any commercial cases more than about 10 or 15 times, so I don’t know yet how long it will last.  

I do the opposite, I make sure the cases are clean, free of lube, and the chamber is clean and free of oil/grease.  I wrap a patch around my chamber cleaning rod and apply some brake cleaner to degrease the chamber before every range session.  I’ve shot many thousands of rounds this way in my LEs, no measurable change in headspace and long brass life.  

This ensures the case is gripped by the chamber and bolt thrust loads are reduced.  But, if you have relatively large headspace, it will overwork the brass particularly if you FL size.  You want to neck size only to get the case to headspace on the shoulder.  Then the only displacement of the case in the axial direction is due to elasticity of the bolt and receiver under load.  

Minimizing bolt thrust loads reduces the fatigue loading of the bolt lugs and bearing stresses on the lugs.   
If your loads are relatively mild, then light lube likely does no harm over the long run.  But, I’ve found the process I use works for me.  


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: July 08 2020 at 9:09am
I have a bunch of HXP & PPU (nny) brass, much of it is on its 6th full power load.
I usually "partial Full Length resize", & anneal the neck after the second trimming to length.

Remington used to be nice, it was my preferred brand, but quality dropped massively over the last few years now I won't touch the stuff, much preferring the PPU (nny) or HXP when I can find it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Zed Quote  Post ReplyReply Direct Link To This Post Posted: July 08 2020 at 9:59am
With all due respect 303Guy. I won't be lubing any of my rounds. All official documentation says not to. 
I'd rather throw away a cracked case than a cracked receiver! These rifles are old; some have seen a lot of action; no point over stressing the old girls just to save a few quid.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Posted: July 08 2020 at 11:18am
Zed is right of course, I just didn’t want to drag out this argument, it caused a blow out and banning of a member over on another forum, a hot topic.  Which is why I said it’s likely OK for light loads, given that bolt thrust increases by about 40% with the case immersed in oil and immediately chambered.  

Lubing cases even changes the MPI on the target indicating the action is flexing more with lube.  See Reynolds book, he gives the test data on this.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Goosic Quote  Post ReplyReply Direct Link To This Post Posted: July 08 2020 at 11:45am
A form of hydraulics and not the good kind. britrifles,  you would not be dragging this out,just solidifying what is already known about lubed cases in a rifle chamber.
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