Afer a few months hold up on this project I have now picked it back up! I've done some more detail on the gun and started the drum magazine.
I used a circular template to get the rough size for the drum, then I drilled a hole in the middle of it, and using sandpaper I smoothed it out, kind of like a wood turner. Then I used some sculpting tools and made the grooves while the drum was spinning around, that way I would get consistent grooves all the way around. The groves were finished with folded over sandpaper.
It is getting there, some more details on the stock and barrel and a few more details on the drum and it should be done. Will post more pics soon!