today after returning from the range i noticed alot of carbon on the bolt face while doing a routine cleaning so i decided to strip and clean the bolt,it seemed like an awful lot of blow by was getting through between the bolt and barrel, so i stoned the bolt face and found it far from being a machine fit,lots of high spots so after a bit of polishing on the arkansas stone and a short time later i put everything back together and headed for the basement range--100rds later i inspected the bolt again and it seemed to be alot cleaner than usual--it got cruddy after one mag before,now it seems to stay clean longer and even feels different (like more ooomph behind it)---some thing to ponder.