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Old 02-05-2012, 23:04   #5
cole
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Quote:
Originally Posted by Zombie Steve View Post
Gas coming around the primer is usually a pretty major sign of overpressure. Might help if you shared your load data with us. I'm a little saucy after the super bowl fiesta, so I'll re-read this in the morning.
I've run Unique, 700x, BE, Solo 1000 and TG (and maybe some others?) from <1000fps to (a handful at)1200+ FPS with 115gr and 124gr FMJ, 147gr (~900-950fps) and 125gr LRN (<1000fps), and 125gr plated. I've had brass barely dribble out of the gun to those that fly out with purpose. Has not mattered (but I can say more loads have been weaker). No signs of overpressure, brass has seen 1-2 reloads and load data is well within specs given bullet, charge and OAL. I've run too many loads to list them. We're talking >40k rounds over many years (mixed SPP (lots), SPPM (lots), SRP (few) and SRPM(few)) in a variety of 9mms, but mainly Glocks in high volume shooting. I've had this ring, or marks on the breech, to varying degrees in all my high volume 9mm guns that have run lots of SPPM. Again, I never sort brass by times fired or headstamp, but I have >30k in 9mm brass so brass does not see tons of reloads anyway. Maybe I just suck reloading, and always have then it would seem, but my money is on the use of SPPM, SPR and SRPM, and those that have run high volume, mixed headstamp 9mm with SPPM, SRP or SRPM can make the best comparison. I've recently been shooting hotter loads (~1150-1200fps w/ 124-125gr vs. 1000-1100fps) so we'll see if that changes anything, though it may take a few thousand rounds to tell.

Quote:
Originally Posted by Colorado4Wheel View Post
The Rifle primers may not be sealing well due to lack of pressure and then gas leaks past and causes the cutting.
Most of the cutting has been with SPPM. I've got >20k with those and less than 1k with rifle primers in 9mm. I agree with the pressure seal as the clear cause. I've run 9mm loads weak and (a few) hot. Does not seem to matter, but most loads have been weak-mid. I don't run real weak loads any more. I think the harder cup of the SPPM, SRP and SRPM has something to do with it indeed. And, not sorting brass by headstamp can't help. I can say it happens in the 9mm hammer-fired CZ and Beretta too, but I've not run those in high volume with SPPM like Glocks and the marks have been very slight and hardly noticeable. Regardless, it's only an issue using SPPM, SRP and SRPM.

Quote:
Originally Posted by fredj338 View Post
It takes very little tolerance gap to get gas blowback. Why brass w/ enlarged pockets should be tossed. Your theory about smaller flash holes is interesting, but I am betting improper primer fit + high pressures.
Low pressure and high pressure loads (based on velocity and published load data) seem to get the same result using SPPM, SRP and SRPM, but I've not shot as many high pressure loads. I do not have a tool to measure CUP pressure so have to go by velocity, load data, felt recoil and appearance of primers. All are within norms. I agree it's a primer vs. primer pocket fit issue, and think the harder cup plays a part. The smaller flash hole theory is just conjecture on my part since SPPM .45acp loads have not (yet) had issues. With >30k of 9mm brass, and the way I cycle through it, most brass has only seen 1-2 reloads. It's all mixed headstamp though. I wonder if SB brass would solve it actually as those suckers are tight. Honestly, I've not worried too much about it, and it does not bother me much on my range/game beater Glocks, just thought I'd share with the class.
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Last edited by cole; 02-16-2012 at 10:27..
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