[quote=Gisk]
2: Gun blows up.  No more gun, and serious injury to character.
3: Fail 
4: Fail
5: Fail
6: Fail
7: Fail
8: Succeed
9: Succeed
10: Succeed
11: Succeed
12: Succeed and can fire again immediately. 

A little less than fifty fifty(skewed in favor of failure) and extreme results on either end.
[/quote]

That sounds like it works to me. Whatever you think is most fair for you! And don't forget the possibility of rolling your Power Number! :) Just remember that you'll also need to roll for your action's success, so after you fire, you'll need to follow the regular roll scale for whether or not you hit the enemy or actually do whatever you were trying to do.