Just wanted to close out the thread on this.
It turns out that it is the damage to the bolt tip that's causing the leak. The 017 o-ring isn't able to keep it sealed.
I got a couple of different 017 o-rings from paintballgateway, one of them having kind of a square cross section. I put that one in with some dow33 and the leak stopped. I'm thinking that the o-ring causes a little more drag, but at least it doesn't leak anymore.
I have a new bolt coming, but I played a day with the square o-ring and it worked like a champ.