I just came across this:
https://www.youtube.com/watch?v=Zw-o3p4ZMtE
The guy is using extended mags, not a drum, but look at what a Glock will do if it’s “suitably modified.” I know you can possess something like this in Arizona if you have a Federal License.
That’s a Glock 18 machinepistol with a 33 round magazine. We call it the happy stick. The magazine is not restricted but you’ll need a Class 3 FFL for the Glock 18.
The drum is more compact and hold 50 rounds.