I have a Gary Schnieder 6mm barrel chambered in 6mm mach 4 it is finished at 27 inches and has a 1 in 10 twist barrel has a had around 200 rounds down the tube, I am thinking about rechambering in 6mm norma br or 6mm ppc and am hoping to have a finished barrel length 22 to 23 inches.I'm looking to shoot 70 to 90 grain bullets not looking to build a speedster just an accurate 300 to 400 yard gun any suggestions?