.50 A.E.'s suffer from the same reservations that the .44 mag does for self defense: slow shot-to-shot recovery, and over-penetration. Something about great big bullets at magnum velocities, I suppose.
Platform choices are severly limited. Freedom,s SA's, or Bowen conversions on the Ruger DA's for revolvers. The Desert Eagle, the L.A.R Grizzly .50, or the AMT Automag V for autos, not including the rifle set-ups.
Eagles are tanks. Grizzly's are 1911's on steroids, and are also tanks, albeit lighter ones. Automag V's are AMT's, which is hard to call an achievment.
I have an Automag V. It is the lightest of the auto .50's at 49 ounces and comes factory ported to help deal with recoil. In my example, it's not quite enough, and the gun is reliability-challenged. It suffers from a variety of recoil-related issues with extraction/ejection, feeding, and unplanned slide lockback. The slidestop has a large spring plunger and detent, and it STILL pops up during the violent cycling sometimes. The gun is plenty accurate, but it operates as if it went into production before all of the engineering bugs had been completely ironed out. This and AMT's rather colorful reputation for spotty quality control probably helped this model to achieve poor sales and subsequent discontinuation.
Even now, Grizzlies and Eagles sell for around $1000, but the most I've seen on an A-M-V is $700. However, A-M-V's are a lot less common than Eagles or Grizzlies, and the weight difference is substantial. I certainly have no wish to dispose of mine, reliable or not.
H_R_G