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.45 ACP cases shorten with use


Loophole LaRue, SASS #51438

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The conclusions that the author draws from this test are a little shaky in some spots, but some interesting data is in his report.

 

But it's safe to say that this test shows:

1. .45 auto cases shorten on firing, but only in the case head/extractor groove area (not the body of the case)

2. this case head deformation during use makes the primer pockets shallower as they are shot, as well as deforming the case head/extractor groove.

3. After about 17 of this test's full-pressure loads, Starline case overall length shortened down to SAAMI minimum.

4. But, additional load cycles still produced functional ammo for at least a total of 50 full-pressure loads, when the primer pockets got so shallow as to prevent safe primer seating.

 

Now, just how fast (and how much) cases would shorten at our generally lower chamber pressures, would be a guess.

 

I'm satisfied that loading .45 auto brass at least 25 times would not be a cause for concern. I know that I toss out brass when the head gets as ratty looking as some of the test brass did.

 

Thanks for sharing that article.

 

Good luck, GJ

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If you want to waste enough time and effort to do the testing, you can confirm that ALL straight wall cases shorten with heavy use. As long as the crimp die will continue to crimp the cases there is no real issue.

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Been load'n .45acp for about 50 yrs. That article is a solution, looking for a problem.

Respectfully,

OLG

Lump:

 

No "problem" raised, no "solution" proposed; just an extended test to see what happens with prolonged time and use.

 

The author is a NRA certified reloading instructor; he was my first reloading instructor. I just thought it was interesting.

 

LL

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I thought it was interesting also, thanks for sharing.

 

I knew the cases got shorter but assumed it was on the mouth end due to repeated slamming into the chamber. I guess I could have reasoned that the head end was getting shorter since I have a bunch of old military brass I've been loading since the '80s and I can no longer read the headstamps on a lot of them. I'll just keep loading them till they split. I haven't experienced the problem with the primer pockets getting to shallow to seat properly. I load them to IPSC major power factor and while not exactly full pressure, still pretty stout.

 

Next time I load some I'll check the length and see if they're under the SAAMI minimum. I thought they only shortened up to a point and stopped, which I guess they must since some of my old brass would be pretty small by now.

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The .45acp is a very low chamber psi round. I have never had any issue reloading it. Now, what he said could well apply to .40 S&W and .38 Super. I also load those. The bigest case issue I run into is the varience from one maker to another maker on OAL and wall thickness.

OLG

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The straight wall cartridges that have rebated rims will shorten with firing because the extractor grove is unsupported. Looking at the side by side image of the fired and unfired cases you'll see that the conical section of the rebated rim is shorter than the new case's. To test the hypothesis that the shortening is caused by the slide hammering the case against the step in the chamber, the test should be repeated using a single action revolver. I am sure that the results will be repeated except the rim and extractor groove wouldn't be chewed up.

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