Originally Posted by DarkRipper
I don't have my bolt in front of me, is that the blue oring? I just use the orings in the repair kit and don't have issues.
No the blue one is a 014, the one he's referring to is a orange 017.
and No it's not a speical kind of oring, a regular 017 will work fine.. as to why yours is square edged im not too sure, may be a bad oring? you shouldn't need to replace it unless it's leaking
there is like 2-4 in your dm12 parts kit. most all orings you need to rebuild your bolt is going to be in the dm12 parts kit that came with the gun