I'm really struggling with my 112 Magnum Target single-shot 338 Lapua. I'm still trying to find a good load for it, probably about 250 rounds through it so far. The only change I've made has been swapping the factory brake for an APA Fat B* muzzle brake. It appears to be concentric - cannot see it from looking through the barrel from the chamber side.

On a good day, it works well enough to get 3/4" groups at 100 yards and 5 consecutive hits at 1000 yards, so I don't think the rifle is inherently inaccurate. On a bad day, it won't even hit the paper at 100 yards. Yesterday I shot 15 rounds using a load that had been a 1" group last time, not a single hole in the target.

I've checked:
  • Crown has no nicks or scratches
  • Scope rings are tight (ARC M10 rings, 55 inch/lbs)
  • Picatinny rail is tight and blue locktited (EGW HD steel, 8-40 screws at 20 inch/lbs per EGW spec)
  • Laminate stock is factory, pillar bedded and torqued to 35 inch/lbs


I'd love some ideas on what might be wrong.