wally
Member
The Garand is .30-'06 by design, "remaking" it to .308 and having problems is on the makers, not the ammo!I thought I just mentioned some in post 23. Unless there not verified enough.
The Garand is .30-'06 by design, "remaking" it to .308 and having problems is on the makers, not the ammo!I thought I just mentioned some in post 23. Unless there not verified enough.
Even if the handloader uses powder not fast enough to keep port pressures down to safe levels while peak pressure is still within specs?The Garand is .30-'06 by design, "remaking" it to .308 and having problems is on the makers, not the ammo!
"...port pressure..." In an M1 is another invention of the Internet. Came along when the assorted Garand pundits could not prove the claims of the ammo alone(primarily the bullet weight only) damaging rifles.
"... Many M1's were damaged by high port pressure..." What documentation proves that? Not anecdotal evidence.
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"... Many M1's were damaged by high port pressure..." What documentation proves that? Not anecdotal evidence.
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I thought I just mentioned some in post 23. Unless there not verified enough.
Those loads damaging Garands were not "hot" if you mean way over spec'd peak pressure. Their pressure curves had normal safe peak pressures but higher average pressures for each mIcrosecond bullets were going past the gas port. Quite a bit more than 10K psi max. Some were estimated to be well over 15K psi.
Andrew, nice pictures, but there's a popular misconception shown.
All rimless bottleneck cartridge cases correctly dimensioned have headspace less than chamber headspace; there's a couple thousandths clearance. When fired, their shoulder is hard against the chamber shoulder. Firing pin springs drive the pin hard enough to set back shoulders a thousandth inch or more. There's a space between bolt face and case head called "head clearance" when such cases are fired.
As the case expands, it grips the chamber wall at the shoulder first (thinnest wall there) then moreso towards the back. That stretches the case body a little bit as the case body contacts the chamber body wall a little over time. It stops when the case head's hard against the bolt face.
Virtually all case rupures are about 1/10th inch forward of the case extractor rim as that's where the most amount of work hardening happens as cases are fired, resized then fired again.
With cases and chambers properly dimensioned, none are held against the bolt face by anything when fired. There's enough clearance to the extractor claw to let that happen. Otherwise, the extractor claw gets stressed by case rim contact and eventually will break from metal fatigue. There has to be room for case heads to slide into extractors when chambered. If there were forces somewhere to pull the case back, they would hinder case head easily going into battery on the bolt face.
I don't see how this is in disagreement with the post quoted....Bart,
From personal experience I will agree to disagree on this one.
I fixed a friends 7.62mm Israeli Mauser that was inaccurate. Brought the rifle from 6" to sub MOA. In this process I noticed that I was getting signs of case head separation after as little as 3 firings in Norma cases. Failures as early as 4 firings. After some research I found a technique to dial out the excessive headspace during sizing. This cured the problem and the owner now can utilise his case for 10 firing before he automatically discard these
Yes there is generally always headspace but when forming 7.62 brass with .308 dies the headspace problems are exacerbated. Here are some of the cases. I have never had case head separation on any other calibres, why? They all have headspace.
Many people shoot 7.62 and do not reload so the problem is not often observed