There are a few others of us over on AR
planning on building 4 bores.Actions are hard to get.
I have setup a way to make 4bore case from 20mm brass.We have Badger barrel setting up to make 4bore barrels,
350 bucks each.This is a 4bore of .998 diameter bulletso as to use the 2000gr bullets Naval ordnance makes.I plan on later for a test rifle using a converted state arms
bmg bolt action.We also want to find an economical
break or falling block to build them on.Ed.