I have a Beretta A390ST with about 30,000 rounds through it. The modifications to it are a lengthened forcing cone, porting, and the trigger pull and creep adjusted by a gunsmith. I thoroughly disassemble and clean the gun every 700 - 800 rounds or so, and am well versed in how and where to lubricate.
Besides breaking the occasional connecting rod (2 in the 4 years that I have had the gun), I have not had any problems. Last weekend, I started getting a jam about every 3rd or 4th shot. The hangup would occur as the bolt was trying to close with a live round, sometimes on loading, and sometimes after the first shot. The shell would stick about 1/2 way into the chamber, and I would have to forcibly pull back on the bolt carrier handle to get it loose and let it slam home. It sometimes took a couple of tries before the bolt would close completely on the live round.
I use only factory ammunition, and the hang ups occurred evenly between the Federal Gold Medal and Winchester AAs that I use. The shells were fresh, and had no swelling or defects that I could see. I tried some of the same shells in a duplicate gun, and had no problem.
I completely disassembled the gun, and could not find any obvious problems. I re-scrubbed the chamber, and then swapped out parts from a duplicate gun 1 piece at a time to try and isolate the problem. The recoil spring in the stock appeared OK, but I did not disassemble it. Instead, I went ahead and started out by replacing the entire receiver assembly (sans the bolt and trigger assemblies). Nothing seemed to make any difference until I replaced the entire bolt assembly, and now it seems to work OK when I function test it. I could not find any obvious defects in the old bolt, but am wondering if shotguns require headspace adjustments. I will be back out to try shooting it this weekend, but am still stumped as to what could have caused this.
Any ideas?
Thanks,
Bud
Besides breaking the occasional connecting rod (2 in the 4 years that I have had the gun), I have not had any problems. Last weekend, I started getting a jam about every 3rd or 4th shot. The hangup would occur as the bolt was trying to close with a live round, sometimes on loading, and sometimes after the first shot. The shell would stick about 1/2 way into the chamber, and I would have to forcibly pull back on the bolt carrier handle to get it loose and let it slam home. It sometimes took a couple of tries before the bolt would close completely on the live round.
I use only factory ammunition, and the hang ups occurred evenly between the Federal Gold Medal and Winchester AAs that I use. The shells were fresh, and had no swelling or defects that I could see. I tried some of the same shells in a duplicate gun, and had no problem.
I completely disassembled the gun, and could not find any obvious problems. I re-scrubbed the chamber, and then swapped out parts from a duplicate gun 1 piece at a time to try and isolate the problem. The recoil spring in the stock appeared OK, but I did not disassemble it. Instead, I went ahead and started out by replacing the entire receiver assembly (sans the bolt and trigger assemblies). Nothing seemed to make any difference until I replaced the entire bolt assembly, and now it seems to work OK when I function test it. I could not find any obvious defects in the old bolt, but am wondering if shotguns require headspace adjustments. I will be back out to try shooting it this weekend, but am still stumped as to what could have caused this.
Any ideas?
Thanks,
Bud