JAZ-

If that rifle were here (knowing what we know about this limitation via modern commercial 20ga hulls) I'd have it at the lathe making a die for magtech brass right now or sooner!

Do you have a lathe or a good machinist?
The work is simple, and it can get you running far sooner than RMC can ship custom cases.

You should call me.
Same old number.

Cheers
Tinker