How many shots do you fire before cleaning? A high pressure and high velocity round like the .22-250 will leave quite a bit of copper in a non hand lapped factory barrel. How fast you shoot and how hot you allow the barrel to get before cooling greatly affects copper deposits and chamber throat wear. I suspect you will need to seat the bullets farther out because of throat erosion, and you will need to step up your cleaning regimen (cut down on the total number of shots between cleanings). I try to rotate between different rifles when PD shooting, so that no rifle gets too hot. You might also want to have the muzzle re-crowned by a competent gunsmith. If you are not using a tight fitting bore guide for the cleaning rod, you can wear the barrel crown, leading to loss of accuracy. Good luck with it.