Xausa: I remember that very photo! It should be noted that the old German 13mm anti-tank round as fired from the Mauser single shot was said to be a grim experience indeed and the .50 BMG is quite similar in performance.

Shooting one with one of the current crops of brakes is no problem. Recoil is not that great, though muzzle blast is almost atomic.

Yes, the spotter round is one and other totally wildcat rounds exist, too, but require such a massive action that if the case is shortened too much it makes more sense to go with a smaller case that allows for a much less obese action.

Szihn, the guns are expensive, but shooting them is surprisingly cheap. Various milsurp components can be had for less than those of many other big bores.