I have a 30 Cal. 15” Contender Bbl. with a 1-8 twist. It is supposed to be a Shelen match bbl. To date, I've tried getting it to group useing several 200 +- gn.cast bullets as well as 150,168 & 190 gn.Match bullets with no success. All loads were between 1050 and 1200 FPS according to the loading data I got with the Bbl.and there was no leading after shooting the test loads.
I've read ere about rolling bullets in 400 grit. valve grinding compound, both cast "J” bullets. BUT there is where the water gets muddy, I've read that 4 or 5 should do, and I think I remember reading to shoot 20 impregnated bullets, at low speed, clean and re test .???????????????????????????????????????????????????????????.