9mm brass stretch?

Reloader2 · August 3, 2013, 04:46 PM

I'm new to reloading for the 9mm. Is it typical to have much brass stretching requiring trimming of the case with this cartridge?

BillM · August 3, 2013, 04:55 PM

No. Case trimming is a waste of time on straight pistol cases (and
those with a slight taper like 9mm).

SL1 · August 3, 2013, 06:53 PM

In short auto-loader cases like 9mm, the brass length typically DECREASES with use. The main reason is that wall near the base of the brass expands and the sizing dies do not fully squeeze it back to original diameter, so it is a little wider and a little shorter. The pressure is usually not enough to actually stretch the brass by pinning the case walls to the chamber walls and stretching the head back to the bolt or slide face, like what we expect for bottleneck rifle cases. Even bottleneck pistol cases like 357 Sig seem to get a little shorter with use.

Although you read that cases like 9mm headspace on the case mouth, that is often not what is really happening. If the case is really too short to do that, the extractor still holds the case back well enough that the firing pin can set-off the primer.

So, you really don't need to trim those 9mm cases, and you don't need to worry about their lengths.

SL1

Ozzieman · August 3, 2013, 07:31 PM

The only pistol cases I care about length are the 44 magnums I shoot in my bolt action Ruger and that’s for uniformity in seating and crimping.
9mm since I taper crimp I don’t even measure them.
Look for cracked case mouths, don’t over bell and watch out for loose primer pockets and you’re good to go.

Jim243 · August 3, 2013, 10:31 PM

The only ones you may want to check are revolver cases 38 Spl, 357 Mag, 41 Mag, 44 Mag, 45 Colt. This is due to setting the crimp to the cannelure and insuring that they are all the same so that one of them will not jam the cylinder.

Jim

WESHOOT2 · August 4, 2013, 07:15 AM

I believe the specific chamber ignition occurs in a significant influence on case condition, to include final fired case length.

I mean, since no two chambers are alike.......

deadeye1 · August 4, 2013, 03:06 PM

There are a few times when trimming straight wall pistol brass is necessary, such as when loading .357 mag with hornady FTX bullets. Shorter trim length than usual to allow proper OAL and still be able to crimp in the cannelure. Other than that i dont trim straight wall cases.

August 3, 2013, 04:46 PM	#1
Reloader2 Senior Member Join Date: June 18, 2013 Posts: 263	9mm brass stretch? I'm new to reloading for the 9mm. Is it typical to have much brass stretching requiring trimming of the case with this cartridge?

August 3, 2013, 07:31 PM	#4
Ozzieman Senior Member Join Date: December 14, 2004 Location: Northern Indiana Posts: 6,117	The only pistol cases I care about length are the 44 magnums I shoot in my bolt action Ruger and that’s for uniformity in seating and crimping. 9mm since I taper crimp I don’t even measure them. Look for cracked case mouths, don’t over bell and watch out for loose primer pockets and you’re good to go. __________________ It was a sad day when I discovered my universal remote control did not in fact control the universe. Did you hear about the latest study.....5 out of 6 liberals say that Russian Roulette is safe.

August 3, 2013, 10:31 PM	#5
Jim243 Senior Member Join Date: January 5, 2009 Location: Just off Route 66 Posts: 5,067	The only ones you may want to check are revolver cases 38 Spl, 357 Mag, 41 Mag, 44 Mag, 45 Colt. This is due to setting the crimp to the cannelure and insuring that they are all the same so that one of them will not jam the cylinder. Jim __________________ Si vis pacem, para bellum

August 4, 2013, 07:15 AM	#6
WESHOOT2 Senior Member Join Date: February 20, 1999 Location: home on the range; Vermont (Caspian country) Posts: 14,324	discrepancy reasons I believe the specific chamber ignition occurs in a significant influence on case condition, to include final fired case length. I mean, since no two chambers are alike....... __________________ . "all my ammo is mostly retired factory ammo"

August 4, 2013, 03:06 PM	#7
deadeye1 Junior Member Join Date: August 4, 2013 Posts: 1	There are a few times when trimming straight wall pistol brass is necessary, such as when loading .357 mag with hornady FTX bullets. Shorter trim length than usual to allow proper OAL and still be able to crimp in the cannelure. Other than that i dont trim straight wall cases. Last edited by deadeye1; August 4, 2013 at 03:07 PM. Reason: added sentence

August 3, 2013, 04:55 PM	#2
BillM Senior Member Join Date: January 20, 2009 Location: Amity Oregon Posts: 791	No. Case trimming is a waste of time on straight pistol cases (and those with a slight taper like 9mm).

August 3, 2013, 06:53 PM	#3
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	In short auto-loader cases like 9mm, the brass length typically DECREASES with use. The main reason is that wall near the base of the brass expands and the sizing dies do not fully squeeze it back to original diameter, so it is a little wider and a little shorter. The pressure is usually not enough to actually stretch the brass by pinning the case walls to the chamber walls and stretching the head back to the bolt or slide face, like what we expect for bottleneck rifle cases. Even bottleneck pistol cases like 357 Sig seem to get a little shorter with use. Although you read that cases like 9mm headspace on the case mouth, that is often not what is really happening. If the case is really too short to do that, the extractor still holds the case back well enough that the firing pin can set-off the primer. So, you really don't need to trim those 9mm cases, and you don't need to worry about their lengths. SL1