IIRC, auto-mags were high end, and rare even in the 70's. As an auto round goes, it really hasn't been surpassed. The auto-mag certainly hasn't been surpassed in beauty, that's for sure.
Grizzly made a more compact .44 magnum version of the 1911. Maybe he would carry that as a backup;-)
I like the .460 Rowland for a movie gun. The muzzlebrake and flash would be good for a movie pistol. It also equals the .44 magnum in power, with lighter bullets, or close.
Still, "it's the most powerful handgun in the world."
Means a .500 right now. Keep in mind Dick Casull and Linebaugh where building .454's and 45 Colts nearly equal the .454, so at the time, my friends and I got a bit of a chuckle out of Harry's line. Should have been,
"The .44 Magnum. It's the most powerful PRODUCTION handgun in the world."
Kind of looses something in being accurate, however.
So, I guess you have to look at two things:
One is the common carry gun, the .44 magnum, and
TWO: the special party guns, like the auto-mag and the .458 Win mag.
For number one:
Some San Francisco Police officers STILL carry the original carry guns they were issued in those times, the Model 57 .41 Magnum. That may well be the most powerful issue hand gun ever.
I like to think the .500 Linebaugh Maximum is the most powerful real handgun cartridge. Loaded insane, it will push a 525 grain bullet nearly 1550 fps.
That's a bit over 3000 ft-lbs of energy, IIRC. The bigger case gives more powder capacity then the .500 S&W. It was designed to operate at lower pressures then the smith, but, for special situations, it can be loaded hotter.
Of course most people wouldn't want 82 ft-lbs of recoil, so the .500 Linebaugh, "short", gets the call as a 'special' round.
With expanding bullets, you get an expanded bullet the size of a 2 bore rifle:
The above is a measly 275 grain speer, in .475 Linebaugh. It moves at 1560 fps out of my 7.5" FA 83. It has been known to leave 4" holes in deer.
Doesn't penetrate like the heavier bullets, but the initial impact would make a Hollywood director very happy.
Similar, but bigger bullets in the .500 Linebaugh would make great 'special'
loads.