[IllinoisCoyoteHunter]

You are pushing them too fast. I would start by slowing them WAY down and slowly woking up. You generally can't push cast rifle bullets to jacketed velocities...even with a gas check. Try a load that will get you in the 1300-1500 fps and work from there. You will find a load that is accurate, but it may not be a speed demon...this is a limitation of cast rifle bullets. You REALLY, REALLY need to slug your bore because an undersized bullet, especially at that velocity...or even way slower, will shred your bullets....thus the lead fowling coming out the end of the barrel. An undersized bullet will not engage the rifling properly and the lead is stripped from the bullet by the rifling. But, I would say that your main, maybe only culprit, is your excessive velocity. Have you thought about pan lubing those bullets?