I would be very grateful for opionions on this and suggestions for possible cures:
Rifle is a wood stocked Heym SR21 in .308. Not threaded. About 6 years old, lightly used - about 30 rounds at most per year. Well looked after and cleaned regularly. Rifle came with recoil lug and first 2 inches of barrel glass bedded from factory.
Until this week, shot very accurately, though with a caveat: Cold bore shots grouped with over-lapping holes. Then Showed about an inch of shift in PoI when shot with a hot bore, but hot bore groups still around an inch, below and slightly to right of cold bore group.
This week, it started shooting very erratically: groups opened up to over 6 inches, with no consistent pattern or stringing. Shotgunning.
Tried everything: switched to a known good scope. Tried 4 different types of ammo. Stripped gun to components, cleaned everything, reassembled and tighted everything. Deep cleaned bore. Got someone else to shoot it. Shot off bipod and bags. Shot with cold bore or hot bore. All the same- large, unpredictable groups.
The only thing I found that might explain this is the front action screw: it looks like it had been cross threaded at some point. It still tightens, and everything seems firm once the screws are done up. So: is a slightly damaged action screw a likely explanation for what I'm seeing?
I'd be very grateful for help: this is a very beautiful gun, and one that was capable of superb accuracy, so it really irritates me that it isn't shooting right.
Rifle is a wood stocked Heym SR21 in .308. Not threaded. About 6 years old, lightly used - about 30 rounds at most per year. Well looked after and cleaned regularly. Rifle came with recoil lug and first 2 inches of barrel glass bedded from factory.
Until this week, shot very accurately, though with a caveat: Cold bore shots grouped with over-lapping holes. Then Showed about an inch of shift in PoI when shot with a hot bore, but hot bore groups still around an inch, below and slightly to right of cold bore group.
This week, it started shooting very erratically: groups opened up to over 6 inches, with no consistent pattern or stringing. Shotgunning.
Tried everything: switched to a known good scope. Tried 4 different types of ammo. Stripped gun to components, cleaned everything, reassembled and tighted everything. Deep cleaned bore. Got someone else to shoot it. Shot off bipod and bags. Shot with cold bore or hot bore. All the same- large, unpredictable groups.
The only thing I found that might explain this is the front action screw: it looks like it had been cross threaded at some point. It still tightens, and everything seems firm once the screws are done up. So: is a slightly damaged action screw a likely explanation for what I'm seeing?
I'd be very grateful for help: this is a very beautiful gun, and one that was capable of superb accuracy, so it really irritates me that it isn't shooting right.