The .50 Action Express
.501") is the cartridge used in the .50 cal version of the Desert Eagle
Looking like a bigger, fatter, .45 ACP the .50 AE delivers more energy than any other autoloading pistol round commercially available.*
Though very popular in the Hollywood sense, the .50 AE is not so popular in the shooting community as it is an expensive cartridge and there aren't a lot of guns that fire that cartridge.
The truth is there is no real need or application for the .50 AE, it was just done to prove that it could in fact be done. Holding only 7 rounds in the magazine, anybody who needs this much power from a handgun is better off shooting a revolver chambered for the .454 Cassul.
Like the gun it was designed to be used with, the .50 AE is more of a conversation piece than anything else.
Don't get me wrong
though, these guns are not toys and are very deadly.
* - the .44 Magnum
and .454 Casull
which are much more powerful are in fact revolver rounds.