my Model 12 has 1:7 twist,
It come from the factory that way or is teh barrel aftermarket?
Push a Match .223 round reliably and accurately to 600 yards?
Yessir it can. With the 1:9 twist, you're probably gonna be limited to the Hornady 75gr HPBT (not the AMAX), but it'll get out there. The 77 Sierras may work - they didn't out of my 10FP.Push a Match .223 round reliably and accurately to 600 yards?