The whole issue with any type of .50 BMG pistol is barrel length. The .50 BMG cartridge uses very slow burning powders that require very long barrels to burn in, and initiate with that slow burn process, high velocity. This simply cannot happen in a 12" or 14" handgun barrel.
I learned my lesson with my Magnum Research BFR .45-70 handgun. The gun is very well made, but cannot produce acceptable velocities with factory ammunition. After much handloading I've come up with good loads, but it isn't something the average shooter would want to tackle from a ballistic standpoint. These guns are fun, make no mistake about it. They just are not the type of weapon you buy, along with a box of ammo, and run off to the range with expecting good results. You are definitely sailing into uncharted waters with these type of firearms! Bill T.