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Old November 30, 2009, 06:02 PM   #1
atxhoghunter
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Elastic Brass?

I have been reloading rifle brass for a couple of years. This weekend started reloading 45 ACP. Someone "gave" me 1000 rounds of range brass they'd cleaned and deprimed. Many different head stamps. Using Lee dies I resized all (as in 100%). Then checked/attempted to trim all with the appropriate Lee Case Trimmer & Case Length Gauge. Problem was that the Case Trimmer would only go into about half the brass, otherwise it was too big. Thought maybe I got a bad Case Length Guide and got another one. Exact same issue. Now I'm checking each case and finding that, even after resizing, I am getting up to 3/1000" variance in the inner dimensions of the brass. The worst offender is PMC brass that runs consistently tight. S&B is the best that runs perfect after resizing. So ... it there some dark metalurgical secret about certain brass maintaining its shape/refusing to resize more than others?
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Old November 30, 2009, 06:39 PM   #2
tom234
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Why are you trimming .45ACP ? IMHO that's a wasted effort and and not needed. No one I know trims straight walled pistol brass. I just shoot them until they crack or you loose them. Bottle neck cases are a different issue.
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Old November 30, 2009, 08:41 PM   #3
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Why are you trimming .45ACP ? IMHO that's a wasted effort and and not needed................. I just shoot them until they crack or you loose them.
Ditto.

I have many thousands of cases for my pistols, and have never needed to trim a straight wall pistol case. I have never seen one "grow" in length, but have seen them get shorter the more they are fired.

Most of my brass is mixed headstamps, but I load them all the same, and have never had an issue with chambering or firing (never bothered to check wall thickness, but have never had issues that prompted me to either). Have you tried loading a few of the different cases with varying wall thickness to see if it will be an issue in your gun?
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Old November 30, 2009, 08:48 PM   #4
Bud Helms
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Why are you trimming .45ACP ?
Because it headspaces on the case mouth. Mind you, I have not had to trim any .45 ACP cases in a coon's age, but that is why they occasionally need it.
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Old November 30, 2009, 09:00 PM   #5
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ATXhogghunter,

When you fire a cartridge the firing pin drives it forward. If it doesn't make it to the end of the headspace from that, it will when the primer ignites and backs itself out of the primer pocket. The flash hole doesn't vent its pressure fast enough to prevent that. What happens next is one of two things: either the whole case backs up, letting the head reach the breech, or, the pressure sticks the case wall to the chamber and the additional pressure that builds subsequently stretches the brass next to the head to let the head back up to the breech. Either way, the primer gets reseated. But only in the second case does the brass come out of the chamber longer than it went in.

Typically, you will find that rounds peak above about 30,000 psi will stick and stretch. Rounds that peak below that pressure typically will not. Indeed, they can actually shorten. That's because, though not stuck, if the load is normal the brass will still expand to seal the chamber, making itself shorter and fatter. Sizing will squirt the brass back toward its original length, but it seldom quite gets there because the die is also slightly massaging the brass rearward. I once ran some .45 ACP through 50 cycles of light target loads. The cases lost an average of half a thousandth per load cycle.

The only reasons to trim pistol brass is to make the mouths the same distance from the heads for crimp uniformity, or for headspacing, as Bud suggests. I headspace on my cast bullets instead of the case mouth, so length is not critical for me in .45 ACP. Making the trim length uniform when applying roll crimps for revolver loads helps accuracy. Taper crimps for self-loaders are less critical. They do allow the brass to last a lot longer, though.

If you want to trim your brass all the same length to start, you may find you have to grind a little off the pin in the Lee tool before it touches them all. Normal trim tolerance is 0.010" for the .45 ACP, and no doubt some of your brass is near the minimum and some is near full length. That accounts for what you see happening with your trimmer, which will be set half way inbetween.
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Last edited by Unclenick; November 30, 2009 at 09:05 PM.
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Old November 30, 2009, 09:15 PM   #6
atxhoghunter
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Thanks for the info

So ... what you all seem to be saying is that I don't need to be as precise with 45 acp reloads as I am with my 300 Weatherby Magnum or 204 Ruger. Makes sense. The .45 will only be used at painfully close range (have a mountin lion issue). The Weatherby and Ruger are for the long shots.

I'll put my teens on sorting brass and see what my .45 will eat. That seems to be all that really matters.

K
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Old November 30, 2009, 09:25 PM   #7
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It's not a precision matter so much as safety. When you trim a rifle case it is to be sure the mouth of the case hasn't gotten so long that it will jam into the chamber throat and prevent the bullet from being released by normal pressure. Hence, the long case can cause a high pressure event.

In the .45 ACP the case can shorten until it would go too far forward for the firing pin to hit if the extractor didn't catch it first. That is called headspacing on the extractor. It is surprisingly common. It hurts lead bullet accuracy, though. Headspacing of the bullet is the best option with lead, provided it doesn't make your cartridges too long for the magazine or to feed reliably.
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Old November 30, 2009, 09:27 PM   #8
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So ... what you all seem to be saying is that I don't need to be as precise with 45 acp reloads...
Not necessarily... Trimming your brass to a consistent length will give you a more consistent crimp. This is especially helpful with range brass that is an amalgamation of all kinds of head stamps and random times-fired cases.


That being said... I bought a 9mm set up for the Lee Zip Trim. (I hate it, but it works in a crude, effective manner for basic trimming.)
I couldn't get the pilot into a single case. Not one! Not even horribly over-loaded, bulged, nearly ruptured, range pick up cases!
So... I just sort by head stamp and approximate condition. I have yet to trim any of the thousands of 9mm cases I have, nor the cases I have given away.

If I need precision, I go with brass known to be once fired, from a single lot.
Everything else just gets whatever the crimp works out to (due to varying lengths), in the crimp groove of my prefered hard-cast bullets.
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Old November 30, 2009, 10:41 PM   #9
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I know this is apples and oranges, but I've loaded some of my 45 LC brass 30 times and NEVER had any growth. I won't trim pistol or ANY straight-walled case. Heavens, if I did, I would be spending ALL of my spare time trimming brass.
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Old November 30, 2009, 10:44 PM   #10
atxhoghunter
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Suggestions for shaving 2/1000"

Looks like greatest peace of mind is acheived if I find a way to grind 2/100"-3/100" off the widest point of the case length guide. (Keeping in mind that my issue is not with the pin fitting through the primer hole, but with the part of the length guide closest to the cutting teeth fitting inside the case mouth). I mounted the guide in a cordless drill and held a piece of medium grit wet/dry sandpaper to it while spinning. No impact on the O.D. Any other suggestions?
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Old December 2, 2009, 02:16 AM   #11
CraigC
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Sometimes you have to trim your straight wall pistol brass just to uniform the lengths to get a consistent crimp. Not due to stretching but manufacturing variations.
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Old December 2, 2009, 03:27 AM   #12
Nnobby45
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I agree with those who say trimming is a waste of time. You will accomplish nothing what so ever. Bet you can't tell the difference in accuracy.

Pistol brass gets SHORTER as it's sized and fired. It doesn't grow like rifle brass and require periodic trimming.

I suspect that different brass thicknesses are responsible for the collet sticking in half your brass. Rifle brass is expanded to the same diameter as the expander ball is pulled up thru it, regardless of brass thickness.

No so with pistol brass, since it's all sized to the same OUTSIDE DIAMETER. Since brass thickness varies in all the different range brass you're using, so does the inside diameter, which isn't sized back out to uniform diameter (like rifle) before trimming.
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Old December 2, 2009, 07:36 AM   #13
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It's been my experience that pistol brass does does tend to get shorter over its life. Also I have never found any new factory brass that actually measured SAAMI spec length. It's all a little short even when new. Don't worry too much about it. Use just enough flare to seat a bullet and just enough crimp to remove the flaring. Your cases will last much longer if you don't over work it.
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Old December 2, 2009, 08:05 AM   #14
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nope

Quote:
....... I've loaded some of my 45 LC brass 30 times and NEVER had any growth. I won't trim pistol or ANY straight-walled case. Heavens, if I did, I would be spending ALL of my spare time trimming brass.
Yeah! +1 about that.
I do appreciate the idea of a more consistent crimp but suspect that it doesn't make much of a difference. Never, ever, in multiple tens of thousands of .45 ACP reloads have I trimmed brass - I don't have that kind of time. I shoot a lot of Bullseye matches and the gun still gets me good scores.
Reload'em. Shoot'em til they split.Toss'em.
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