Here is picture of the 12ga belted cases I made to
test a few loads in. I made it from 55cal belted
Boys case. I reduced belt diameter a little and left
the base the same, which is 12ga size.In picture
first is 55cal, second expanded to .620", third
expanded to .660"(16ga), then two 12 ga ones.
Next is our 12GA FH, and then a 12ga 3.5"
plastic case.A little work in long 12ga FH chamber
with a tool for belt step and it chambers. Ed