I + many others have been using rifle primers [ large + small ] for over 50 years with never one problem that I am aware of - years ago I spoke to at least three manufactures + they all stated that the only difference was the rifle primers had a harder cup material - the compound . brisance , + power were the same except for magnum primers - there is a thread now running on this subject on the CMP forum - I use them in .32acp , .32 s&w , .32 s&w long, .38 s&w , .38 spec. , .38 super , 9 mm luger , + .45 acp . - a firearm with weak main spring might be a problem , but I never have experienced any -