Yes, I removed the firing pin. I cut/ground off the end of the pin to remove the whole assembly through the firing chamber. That's why I had to drill a hole and insert a cauter pin in the end (that's the little hairclip looking thing at the end holding the whole thing together).
Every single super soaker I fixed this way had the same problem- that tiny, tiny little o ring inside wore out and with the seal blown, the gun leaked like crazy out of the firing chamber. Replace the o ring and lubricate, gun works like brand new. The real problem is that there is no way to replace the o ring without removing the firing pin. I came up with a solution to that problem. Cost me a few nickels worth of parts out of a large box of assorted size o rings and another box of cauter pins (thank you princess auto!)
You can see the tiny little black o ring in this photo.
OK I'm going back to homework now.