Mark Serbu with BFG .50 Carbine 
Muzzle of the Serbu BFG .50 Carbine
Mark Serbu with BFG .50 Carbine
Muzzle of the Serbu BFG .50 Carbine
Even better: not only is Mark's BFG available in the usual .50x99mm chambering of the M2 Browning .50 caliber MG, but if you ask him nicely, he'll make it in the shorter .50x77mm chambering of the semiauto M8C spotting rifle used atop the 106mm recoilless rifle as a rangefinding device. Though it's unlikely very many users would find ammo compatability with their antitank gun's spotter rifle real useful- there are a few- there are a couple of other advantages, including lessened recoil and muzzle flash. Either way the *spotter-tracer* projectiles from the .50x77mm can be used for reloading either cartridge, easily identifiable by their blue-tip nose marking. The flash and smoke when they hit is spectacular, as it needs to be for the intended purpose- and incendiary.
And if you want to own a 50 BMG but are worried about it being on the future confiscation list (and can't find a private seller - shold that be permitted in your state) you can buy a 50 BMG upper for your AR15 lower, and it is a non-registered gun part of which there is no official record. (Google "50 bmg upper")
Also, is there any doubt what "BFG 50" stands for? ;-)
