Quote Originally Posted by MustangO3
As for your mounting issues, I think you would have a hard time finding super large primers after the Zombocalypse to reload your 20mm, so I would just skip on the brass catcher. You know, keep it simple.
No sweat there, the 20mm accepts .50 BMG primers although you need to use Loc-Tite or cyanoacrylate to fix in place as they won't fully seat/crimp in the primer cup. A high ROF keep da zombie away!

Some pics for reference...