Took out one of my STG's to the farm for the first shoot after Winter and started experiencing some issues that I never had with this very rifle. I had a couple of double feeds (was using some new clear 10-round Mag's loaded with 5 rounds) and the big issue was failure to extract about every 5-shots. This ruined some pricey ammo. I was quite surprised as I never had any problems with this gun before -maybe 300 rounds thru it prior to this. The gun was clean and well-oiled (maybe too well oiled....) ammo was all new QUALITY stuff ( Hornady, Black Hills, Federal) and after stripping it down everything looked as it should. I can attribute a few of the failure to eject on a "soft shoulder" error on my part (apparently I forget how to shoot over the Winter months) but the failure to extract ?  Did some oil cause the extractor to have a problem, or get into the chamber and swell up around the case?  The case pretty much fell out when the bolt was opened and the gun was shaken a bit..

One thing I,m wondering about is that upon inspection I noticed an area on the receiver / feed ramp is starting to marr. Where the fingers of the bolt lock into the "female" slots it is starting to develop an "edge". Like when you hammer metal and it "rolls" an edge off of a flat surface..... Should I be worried about this ?  Should I file it down ?  Obviously the slots are enlarging.....

Thanks in advance ....

post a pic of the suspect parts and I bet we can help you out....

That sounds like bolt peening, which was a problem.  If you had access to the archives you would see several threads about it.  As I understand, it was supposedly due to an OOS trunnion.  I don't believe it usually caused FTE though.  Hopefully someone more knowledgeable will chime in.  



 

I looked in the archives as you suggested (thank you) and saw a thread with pics concerning the bolt sleeve peening issue. This is not the case with mine. The sleeve looks fine -  its the slots on the trunnion that are getting hammered. I'll try and get some pics up tonight. Thanks for that suggestion too......

There were a few posted problems of the issue you are having and some pics also.. If i remember correctly the slot in the carrier is off in specs and causes the bolt lugs to be out of line with the trunnion lugs, they end up hitting each other as the bolt enters the trunnion.

Can you show us some upclose pics ?  this will help others in the future who may have this problem. Thanks