I inherited a custom .311 7.62x39 14" Contender barrel and a few rds of ammo for it. I have no idea what the rate of twist is, the label on the box says, 7.62x39, IMI brass, 145 gn rebated boattail JSP, Fed primer, AA1680 powder and I can't make out the weight for sure. The bullets are custom made and have a long tapered ogive, they look like Sierra 155 gn Palma bullets with a rebated boattail. From a Ransom Rest, I put 10 rds in the same hole at 50 yds. Does anyone make anything close to this bullet? Either custom made or commercial.