Get online to Dixie Gun Works...

I replaced a drum for a buddy 10-12 years ago, I remember it was a CVA in .54 caliber because I also did the load work up for him and installed a new front sight because some idiot had filed the one on it too short...

If I remember correctly the threads were 1/4 inch coarse...That's what you need to know, find out what threads fit, order a new one and install...Once you get it, you may have to file the threads a tad to get it to line up with the hammer...

Now...If you just want a new barrel...I'd go with a .54 round ball twist (1-66 or 1-72)...Then order a .530 Rapine bag mold and you never have to buy ammo again...A .530 ball with 80grs Goex FFF is deadly on deer...