I like to take the bad shooting Tang safety MkI's off people hands.

If they won't hold zero, it's real simple to replace those dead soft Factory rings with some after market rings or install a Redfield base. that has solvled the problem for every Ruger that I dealt with that wouldn't hold a Zero.

If the rifle won't shoot a group I first try loosening the guard screws and tightening the recoil lug screw. If that doesn 't do it, then I get radical with cleaning the fouling with Sweets. Older Ruger barrels are rough and foul badly. And if that still doesn't do it then I put a new barrel on the rifle and that always does it.