Does pistol brass shrink? > Reloading

Geforce_2

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Posted: 8/10/2026 5:31:04 PM EDT

I've got some 9 & 45 brass that's been reloaded a few times, and it seems like it's getting shorter. How short is ok? The manuals are clear on max length and trim to length. How short is too short?

45 acp = .893 - .898 (per manual)
Mine varies after sizing from about .880 - .889

9mm = .749 - .754 (per manual)
Mine = .739 - .752

Will these lengths be ok for these calibers?

DVCER

SHTF ammo dog

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Posted: 8/10/2026 6:01:17 PM EDT

[#1]

I thought I was an experienced reloader, but I’ve never thought to measure that brass. Probably loaded 40k .45 and never thought to do it.

If life was easy nobody would quit.

fast_fairlane

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Posted: 8/10/2026 6:16:34 PM EDT

[#2]

Have you already resized them?

fastluck13

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Posted: 8/10/2026 6:34:21 PM EDT

[#3]

Yes it do

Geforce_2

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Posted: 8/10/2026 6:40:16 PM EDT

[#4]

Yes, that's after it's been cleaned and resized. Not expanded or trimmed since the last time it was shot.

Rope-A-Dope

Ringer

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Posted: 8/10/2026 7:42:13 PM EDT

[#5]

Tag for explanation of this phenomenon.

I would be curious if short brass would be a crimping problem.

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MarkBinSC

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Posted: 8/10/2026 9:03:06 PM EDT

[Last Edit: MarkBinSC][Edited] [#6]

My Speer 13 manual has a 9mm trim length of 0.744, 45acp is 0.888

What manual are you using?

I have never measured the length of straight pistol cartridges in 20+ years of reloading.

I would not worry about it.

FB41

USMC 1977-1987

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Posted: 8/10/2026 9:52:01 PM EDT

[#7]

I have never measured 9mm or .45 ACP brass in 50+ years of reloading, so I couldn't honestly say whether it shrinks or not. I just load'em until they split.

downrivertrash

Joined: Mar 2004

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TX, USA

Posted: 8/11/2026 12:54:47 AM EDT

[#8]

I measured and trimmed .38 brass for wadcutters so I could crimp consistently. I'm using the same brass so after a few firings I can measure and see if there's changes to length.

Jetpig

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Posted: 8/11/2026 9:10:52 AM EDT

[#9]

Straight walls shrink. Yes.

rn22723

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Posted: 8/11/2026 4:37:41 PM EDT

[#10]

I have read where the idea that hand gun brass shrinks.
I have never trimmed 45 ACP or 9MM and for the most no other straight walled handgun cartridges except some 44 Magnum brass to uniform for crimping purposes.

jme and I am a NRA Endowment Member

Don't be too timid and squeamish about your actions. All life is an experiment. The more experiments you make the better.
R W Emerson

sandspider500

Joined: Jun 2024

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USA

Posted: 8/11/2026 7:59:22 PM EDT

[#11]

I have a few hundred starline 45 acp cases.

They've been fired in a ruger blackhawk about 12-14 times.

That brass is loaded and fired, and comes back home with me, every single time.

Brass that was new, and measured .892, measured at about .884-.885 after firing.

Now, at 12-14 times, after firing, it measures .877-.878.

And when resized, it measures .883

Most people don't hold on to auto loading brass that long.

It does shrink.

The web of the case will expand some after each firing.

Your sizing die never touches that.

Some of the old starline brass measures .478-.479 at the web.

snackle

Joined: Feb 2018

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Posted: 8/12/2026 8:50:31 PM EDT

[#12]

Interesting. This explains the occasional 9mm that I rejected during case gauging because they dropped too far into the gauge. I just assumed it was out of spec from the factory.

It chambered and fired fine though, before I tossed out the brass.

rn22723

Team Member

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Posted: 8/13/2026 2:24:09 PM EDT

[#13]

I have brass that I got back in the late 80's. Most has been lost over the years. But it shows up when I sort my 45 ACP brass.
As was can all agree that straight walled cartridges shrink. Additionally we all shoot it till the case wall cracks or we lose it. I have 45 ACP brass that you cannot read
the headstamp anymore. It is like the energizer bunny it keeps going and going and going

jme and I am a NRA Endowment Member

Don't be too timid and squeamish about your actions. All life is an experiment. The more experiments you make the better.
R W Emerson

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