The aluminum of the bolt oxidized and it's probably enlarged or fused to the tube. Put some break away or penetrating oil down the barrel and let it sit on end for an hour or so. Pull the pump off then find a long allen that fits in the pump arm hole in the bolt. The first mission is just to turn the bolt so you can get the bolt pin out. Hopefully you can get the pin out. If so, use that allen to turn the bolt to loosen it up. Then I'd go with a length of 1/2" dowel down the barrel and try and beat it out of there.
Note: While I would love to take credit for his work, I am not associated with Mad Customs!
Originally Posted by senghing27
You can contact BigMatt-MadCustoms in his MCB forum