Just broke in my second mullerworks barrel Both are of the cut rifled variety I cant say enough good about them they both broke in very fast almost no copper after 2 shots I did a 6 round break in on both shoot clean for 2 shots then shoot 2 and clean twice this seems to be all that was needed. One is an 8 twist in 223 an absolute tack driver its on an origin action jewell trigger in a mcmillan stock second in a 8 twist 6.5 I hate to say it creedmoor I figured I should own one its on a trued 700 jewell trigger and a hs precision stock this rifle has shot everything I have put in it under 1 inch and most under 1/2 moa, consider these barrels when thinking about another build I have used benchmark, brux, bartlien and kreiger for years and these mullerworks are just as good as any of the others