A couple of questions about pins.

The trigger pin is held in place by the spring legs on the hammer.  I don't see anything holding the hammer pin in place.  

What holds the hammer pin in place or would this be an ideal candidate for an Anti-walk pin?

Bushmaster and several other sites have anti-walk pins for Mil-Spec lowers.  What about Colt lower with odd sized pin holes?

Thanks for the info

The hammer pin is held in place by the J-Pin.  The J-Pin should rest in the center groove of the hammer pin and lock it in place.  If you look through the hammer pin hole you should see the J-pin.  If you don't and your hammer pin is walking out then the J-Pin probably broke.

I had a J-Pin break a couple of weeks ago.

Really?  I have an AR10 with a NM trigger and my hammer pin is walking out on it.

I cant wait to take it apart now....

I can't say that is the case all the time but it would be the first thing I would check now.  After about 70 rounds I noticed my hammer pin was sticking out the left side of the receiver.  I was able to push it back in (strange cuz they are always such buggers to install) and continue shooting.  But after a couple of rounds I noticed it was creeping back out so I stopped shooting, brought the gun home, took the hammer out and noticed there was no J-Pin showing when I looked through the hammer pin sleeve.  I could see it at the bottom of the hammer so it didn't fall out completely.  When I called to order a new hammer the lady said, "it happens, not very often but it does happen".  

Let me know what you find.