Cal74: I own a 77/22 Long Rifle. The bolt is split, and the front third does not rotate when the action is cycled. In many rifles this is a non issue. In mine it was, as groups were running about 1.25 inches at 50 yards regardless of ammo.
After some research, I bought a pack of shim stock with about 6" x 12" pieces from 0.002 up through about 0.012." One cuts off a tab, pulls the bolt in half and drills a hole that will let the tab fit between the halves. Next I used a Dremel tool to grind the tab so it matched the bolt profile. Basically a round washer.
One can find instructions for taking the bolt apart elswhere.
I started with a 0.004 shim and it had no effect. I went to a 0.010 shim, and it was very difficult to close the bolt, but the rifle shot lights out. I backed down to a 0.007 shim, the bolt offered slight resistence on closing, and 10 shot groups were nickel to dime sized at 50 yards. Basically, it's a headspace issue, and the right dimension shim will have the bolt face snugged up consistently against the barrel.
I'm extremely glad I discovered that fix, as I was about to spend a few hundred for a new barrel and commercial accurizing job.
Another blessing is that one can easily tweak their trigger springs and sear engagement. I had nearly abandoned my Ruger for ground squirrels, but after the fix, it's a toss up as to whether I use my Anschutz with its 1-ounce trigger or the 77/22.
Like centerfires, all of my 22 LR's are ammo sensitive.
Last edited by 1minute; 11/18/09.
