I've never bought a 9mm factory cartridge and never bought 9mm brass. I've only loaded range pick ups and have never had to trim brass. You should spend your energy doing a plunk test on your completed rounds using the barrel of your gun or a case gauge if you shoot multiple 9mm's. There are occasions where the brass is expanded more than usual at the base and you want to either cull those out after resizing or use a push through resizer because a fat case head can cause a stoppage while you're shooting. Nothing that a squib rod can't pound out but it's still better to catch those rounds before they go into your gun.
TRIMMING 9MM BRASS???
- Thread starter 74man
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EricBu
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- Apr 2, 2021
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Nobody in their right mind trims 9mm. If somebody needs matched brass for comp...they buy new brass. Otherwise, just send it.
Soonerpesek
Member
Yeah, but 30 Carbine brass grows while it’s just sitting in the bucket…!!…..
nettlle
Contributing Member
I only reload straight walled 9mm and 45acp. Does all straight walled rifle brass grow? Just wondering.
LV Gun
Member
357 magnum seems to be the same way it never stops growingYeah, but 30 Carbine brass grows while it’s just sitting in the bucket…!!…..
OS/N
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- Nov 2, 2023
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- 246
As long as they work I wouldn't worry. Slide goes into battery and cases don't stovepipe.
If your shooting matches then I may stick with the same brass make.
Even if you trim and use mixed brass the pressures won't be the same. Too much variation in wall taper/thickness and in case depth/volume.
As long as you use the same type brass the pressure will be okay even with different length cases if you seat the bullets at the same depth and meter powder accurately.
If your shooting matches then I may stick with the same brass make.
Even if you trim and use mixed brass the pressures won't be the same. Too much variation in wall taper/thickness and in case depth/volume.
As long as you use the same type brass the pressure will be okay even with different length cases if you seat the bullets at the same depth and meter powder accurately.
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AS I've come to understand it, 9mm and the like head space on the mouth of the case, which means each time it is fed......slammed......into the chamber, the case slams to a stop as case mouth hits the chamber's shoulder. Case actually gets shorter and thicker over time. Since few if any ever arrive longer than SAMMI max, there is never any need to trim them.
Yep, trim all revolver brass, no auto brass. (Not even it it's shot in a revolver.
)
AJC1
Member
357 is weird it gets out of square for sure but actual growth is meah....357 magnum seems to be the same way it never stops growing
BJung
Member
There use to be an article on the Cast Bullet website (not the castboolit forum) that included accuracy tests with cases trimmed to different lengths. I can't find it now.
Ks5shooter
Contributing Member
No trim for me.Roll crimp only handgun brass gets trimmed.
Atavar
Member
I keep getting stuck on this statement. Can someone please educate me on how case length affects pressure? To my way of thinking so long as you load to a given COAL the bullet is going to be the same distance from the primer regardless of case length. The internal volume is going to remain the same.
The only difference will be how much of the bullet is covered by a longer or shorter case. I can’t see that as significantly affecting pressure.
While the OAL hopefully remains the same, the amount of crimp applied to the case, which applies pressure to the bullet needs to overcome before leaving the case mouth, will vary depending on the length of the case. A longer case will go further into the crimp die, while a short case will not enter as far. The longer case will receive more crimp while the short case will received less.
More pressure from the case mouth will delay the bullet leaving the case and allow pressure to continue to build in the case until it does.
nettlle
Contributing Member
Stretched brass will cause the brass to shove the too long case neck up in the chamber and pinch the bullet. Brass that is over length can be dangerous stuff.
We're discussing 9mm cases here...and in a broader sense handgun cases
Atavar
Member
I can see that being a small difference, but with a taper crimp like we use on 9mm I don’t see it being significant.
That would be your prerogative
When I first got my Dillon, I set it up for 9mm. Got everything together, cases, primers, bullets. I was going to load a lot of 1000 rounds beginning with several hundred. I checked the cases and started to decap and trim them. Then I thought-nah, no flipping way- and merrily skipped those steps. I've never looked back. However, if you feel the urge, go for it. It certainly won't hurt anything.
JohnMc
Member
You can if you really, really want to.
It isn't worth the bother.
It isn't worth the bother.
I'll be mighty impressed by anyone who can shoot the difference between trimmed & squared 9MM cases vs non.
Maybe some Bullseye shooters, but I am not encumbered by such skills. I'm a good, but not great, pistol shooter.
I have proven to myself that a good batch of same headstamp 9MM brass can outshoot a horrid mix of range brass,
even in my hands, and I had so much of it I did just that.
Nothing scientific, but it shoots a little tighter up close and gives fewer "hmm" misses at distance.
Maybe some Bullseye shooters, but I am not encumbered by such skills. I'm a good, but not great, pistol shooter.
I have proven to myself that a good batch of same headstamp 9MM brass can outshoot a horrid mix of range brass,
even in my hands, and I had so much of it I did just that.
Nothing scientific, but it shoots a little tighter up close and gives fewer "hmm" misses at distance.
tightgroup tiger
Member
You couldn't pay me to trim 9mms. There is just nothing to be gained by it.
I understand you don't have that many and most of us here are dealing with many thousands of them on a normal basis, but if there were an advantage to trimming them, we would have found it by now.
Your .750-.740" range is ideal for 9mm, I have found some that measure down to .730"
I set my flaring die up so I can't get a bullet to start at below .740" and just pitch the short ones.
Wasteful? Maybe, but I have enough 9mm cases that I don't have to use them. It's faster for me to do it this way than to sit down and measure each and everyone. I set them aside and deprime them later to recover my primer for later use.
I understand you don't have that many and most of us here are dealing with many thousands of them on a normal basis, but if there were an advantage to trimming them, we would have found it by now.
Your .750-.740" range is ideal for 9mm, I have found some that measure down to .730"
I set my flaring die up so I can't get a bullet to start at below .740" and just pitch the short ones.
Wasteful? Maybe, but I have enough 9mm cases that I don't have to use them. It's faster for me to do it this way than to sit down and measure each and everyone. I set them aside and deprime them later to recover my primer for later use.
That's what I do with auto cases as well, adjust for the "average" and toss
any real short ones that don't get enough flare, but I also toss any real long ones.
jmorris
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- Sep 30, 2005
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- 24,183
I have shot hundreds of thousands of 9mm reloads the only ones I have ever trimmed were the .223 cases, I converted to 9mm shot shells.
This is 10 shots at 100 yards using not only not trimmed brass but mixed headstamp range brass of unknown # of firings.
If I need to shoot much better than that, I pick something better suited for precision than the 9mm and I probably do have to trim those cases......
This is 10 shots at 100 yards using not only not trimmed brass but mixed headstamp range brass of unknown # of firings.
If I need to shoot much better than that, I pick something better suited for precision than the 9mm and I probably do have to trim those cases......
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