which bolt..?

[obiwankabaldi]

I am confused and feel stupid since I never knew there were various configurations for a AR-10 bolt. I have a DPMS upper stamped 7.62 x 51 I have been shooting this rifle for a time with a BCG that I purchased online. Lately the bolt jams and the action will not open. Taking the  bolt apart and checking Headspace I feel that it is way to tight.  I did some research and found that there are 2 specs for bolts. One with a .125" counter bore to face of bolt and another with .129" counter bore to face of bolt. It seems that the .129" would be perfect. Where do I get such an animal if this is true. How do I know for sure which bolt I need?