I done some trading a few weeks ago and got a model 12 223 with a heavy 26 in barrel. It shot around an inch, figured I could make it do better so I went to work on it.
Took it apart, laped the lugs, laped the recoil lug to the face of the receiver, and the barrel nut to the recoil lug. Set the head space to a min. Done a trigger job and the bedded it.
I put a Nikon 6x18 buckmaster on it and loaded a few different loads to try. The thing shot real nice, .15 to .25 5 shot groups every time.
Well, after a few hundred shots, the dang groups started opening up, 1/2 to 3/4 in. I've cleaned it really good, tried everything I can think of. Even rebedded it.
Can't think of anything it could be but the scope but its not like some of the other scopes I've seen go bad. All my other scopes are 3x9, so it's hard to compare.
The loads are the same as when I started lot # 's ect. Everything is tight and to spec.
Any suggestions ?