Are you kidding?
Do you mean there are actually people chambering a 136 year old action designed for low blackpowder pressures for the .50 BMG?!?!?!?!?!?!?
I like Rolling Blocks, and I know that Pedersoli and some others have chambered Rolling Block reproductions in .50-70 Gov't, but unless the action is truly immense, I don't think it would stay closed under .50 BMG pressures.
Doc Hudson >8-0