Miss Piggy took a major dump on Sunday. In the middle of my second 100 rd belt I had not one but three case head separations. Ammo was GGG (Lithuania) headstamped with the NATO cross symbol and it seems to be highly regarded. I could find no reports of case failures with it on line. So if I assume it's not an ammo issue, what can cause a 60 to suddenly develop excessive headspace? Or to fire out of battery?
The locking recesses on the barrel extension are unharmed.
The bolt has the traditional chip out of the left front corner of the top/right lug but the rear faces of both lugs are good. The guide surfaces show some wear and parkerizing is worn on the large diameter of the bolt body in a lengthwise stripe behind the top lug indicating it is rubbing on the trunnion when the bolt goes into battery.
The front radius of the drive lug on the op rod has seen better days; the ridges and burrs have been stoned smooth but this was going to be its last trip to the range. The firing pin drive lugs show some wear but I'd generally rate them as good. All the guide surfaces are intact and show no excessive wear. There is a wear pattern in the parkerizing on the flat on the bottom behind the sear notch but no other damage. (Speaking of which, one of my spare op rods, the oldest one, does not have this flat, the others do. Does this matter?)
I can see no significant damage to the receiver. The trunnion is solid and the welds all appear to be intact. There is very minor wear on the front of the top right and lower left corners of the bolt socket where the bolt has rubbed.
I'm pretty much at a loss here, what am I missing? Absent a definable cause, I'm planning on putting in a new bolt and op rod (which I was going to do anyway after this trip to the range) and switching to a belt of known quality (Prvi Partisan) ammo and seeing what happens. But I'd really like to suss this one out before I do that.
Edited by StrangeRanger, 07 August 2019 - 03:24 PM.