Alright, finally removed that epoxy joint. I burnt the epoxy and let it cool off for a little while. The joint still wouldn't break. I twisted it with a monkey wrench, but I couldn't pull it off. At this point, I ripped the barrel out of the gun (another epoxy joint; why couldn't the first one break so easy

). I grabbed a piece of 3/4" copper pipe, sleeved it on the aluminum barrel (a perfect fit, by the way), and proceeded to continually smash the joint down. Finally, it broke off. I threw it as far away from my house as I could (probably not a good idea in retrospect), and the deed was done.
The gun looked like crap at this point. It was tarnished, thrashed from the wrench, had a broken barrel, and no supports. I polished both the aluminum barrel and the copper chamber, and now both shine really nicely. I just put some epoxy (grr....) on the barrel and slid it into the copper valve, and it is currently drying. I will replace the barrel supports soon and take a few pictures.