I concur on powder choise for the same reasons . That just goes to prove no two identical barrels are truly identical . My 12.5" and 18" both shoot 120 SST at or less than moa but my wife's 16" 5r ARP shoots them into tiny little groups . As matter of fact the best 5 shot group I ever shot was with it at 200 yards . I thought it was a fluke so I tried it the next day and almost duplicated it . Hers doesn't like 90 grains and she likes the SST so much she won't consider cavity back .Factory hornandy SST doesn’t group well out my 16” either. I have a few hundred of these projectiles but haven’t tried loading them yet.
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