Here is some more info on our 2 and 4 bore work,

First picture is the 30mm barrel, that will be our
two bore barrel, with a model pivot and lug
block on it, like you would use to build a break action.
Also in picture is a 2bore case,4bore case, 458WIN.

Second picture is a 2 bore case next to the 27mm
Nato case I build them from.In pic is 3006 for comparison.

Third picture is two 4 bore cases with 2000 gr Naval
Ordnance bullets, and sample 20mm case we build them out
of, and proverbial 06 for comparison..Ed