The first idea for the 12ga FH case built from bmg brass and the name
was from Robgunbuilder over on the Accuratereloading big bore forum.
I just helped make it famous and worked to develope, along with
many others, a variety of applications and guns.That is what
we call it although the barrels are just marked 12ga and the length.
It is in essence a longer 12ga case. I have brass I could make
them longer. The WW2 military had shotgun cases much longer
than ours for starting big aircraft engines.
The long 700 HE belted case is the first one like it
that I know of..Ed