im supposed to be going to shoot my new dpms. i wanted to be checked out on disassembly and cleaning first. with very little help from the pos owners manual, i managed to tear it down. i was very surprised not to find a spring loaded firing pin in a rifle that cost 700 bucks, anyway the koter pin that holds in the firing pin is all screwed up and wont go back in the hole. can i replcae it with a new one from a hardware store? or does it need to be speical? harder? also the bolt locking mechanism has offset teeth its pin can go through both sides, so how do i know if im putting it in wrong? the shorter tooth could be on the bottom or the top. which is correct?