Overpressure Troubleshooting

[627PCFan]

I loaded up a batch of 45ACP rounds for my buddies 625PC. Mixed cases, 8.0 Grains of AA#5 and MBC 230 LRN bullets. The recipe is mid-level from the manual. Primers were Tula LP. Seating depth 1.23 inches. Check out the primers. What I call way hot. I think they would have disassembled a 1911 in short order, but since they were being fired in a 625 we shot them anyway to determine the cause. I saved 10 out of the 50 which were dissassembed last night. The powder drops were a consistent 8 grains even across the ten. In the end, some primers were fine, some where showed slight overpressure, some were straight flatened and smooth and several you could barrely tell where the primers ended and the brass head started. So I think half of the problem is the 45 load data is derived from 1911 style chambers which are looser and something as precision as a 45 revolver would more consistent and "tighter". The other half Im confused on. Could it be 45 case capacities as mixed brass was used?

 

[rcmodel]

Seating depth 1.23 inches.

That is too short for 230 RN.
Mil-spc 230 FMJ-RN would be seated 1.266" - 1.271" AOL.

Lyman #49 shows a 230 LRN & AA #5 seated 1.272".
Start is 6.6
MAX is 8.2.

8.0 grains seated 1.200" would probably give high pressure!

And the mixed brass isn't helping anything as you try to sort this out for sure.

rc

 

[Fishslayer]

I've never seen primers "dished" like that before.

But definitely do what RCModel suggested. Normally I wouldn't expect a couple hundredths OAL or case capacity difference to have a whole lot of effect in .45ACP but if you're using a heavy charge with a shorter OAL ya never know.

 

[gamestalker]

While working in the industry some years ago, a customer came in with the same erratic pressure issue, 45 ACP. He brought with him the remaining unfired cartridges for my inspection. After chamber checking them in his barrel I quickly discovered that they were slipping in past the mouth, which was causing the mouths on some to get pinched in the throat. The primary culprit was over crimp. But because the brass was very inconsistent in length, some were getting excessive crimp, enough to pinch, while others were not.
After correcting the crimp issue he reported to me that all were functioning well.
But considering you were experiencing this problem with a 625, it isn't likely that this is your problem. I would heed RC's diagnosis regarding seating depth.

GS

 

[TheCracker]

Wow. I've seen that in 308 a couple times but never in any handgun load including 44 mag!

 

[627PCFan]

And RC was dead on. Bumped it out to 2.25 and it went away except for a certain type of brass. Must be thicker brass.