Already been throught that

I thought of it a while back.
In a way, you can. Not the BMG as is, but you can chamber the SB2 Ultra Slug Gun to 12 FH, which is the 50 BMG case with the case head threaded and a 12 Ga size rim screwed on, then blown out straight.
While this does give a fair amount of rear thrust, chamber pressures are much lower because of the massive size and slow rifle powder used.
Even in the 3" chamber, I've put some hairy loads in it.
I have started to flex one of my frames though.
Lately, Ed has made up some loads using the 55cal belted
Boys case. That' a belted 50BMG case and the devil to find now. I guess RMC will make them up in you wanted.
So the answer is NO BMG...but yes to sort of.
