Bought mixed head stamp brass and couldn't get some of them to accept primers, if I got some started they wouldn't seat properly. Finally noticed the problem brass was all Marked Win NT plus P. The original primers were set in with an extra small circular press mark on the brass just barely outside the primer pocket. Wound up mounting a drill in a vise and just used my fingers to rotate the cases to ream the pocket so the new primer seats like normal. Took apart a few cartridges before I tumbled to the problem. Do all plus p need special attention in order to seat primers? Is this a newby error? Before I figured it out I ordered a RCBS universal hand primer tool thinking that might offer more tactile feed back and unlike a multistage press it would be easy to feel/look to see the primer before going further.