Been shooting 150-155gr bullets for years through mine. Even shot 168 and 173gr rounds at first, but they don't do any better as far I can tell. No dramas or headspace increases or anything! The scope is best calibrated w/ the lighter bullets for me (in meters), heavies seem to match the graduations in yards (but not quite- too flat shooting). Up close its hard to tell - past four hundred things get more noticable.