Finally have the .500 AHR in hand; even better condition than the pictures and description with only minor storage marks, the rifle appears to be as new and fired little if at all. I think this is one of those rifles that the original owner either:
1) shot it 3 times, went OMG!.......and put it away
-or-
2) bought it for the “I’ve got a bigger gun” bragging rights and possibly never fired it; this could be, because there was no ammo or empty fired brass with the rifle.

The original description to me was a little off on weight, according to my scale the rifle rifle weighs 10lbs 12oz with empty magazine. The magazine holds 3 down.

Have brass, bullets, and dies in hand so got to shoot it yesterday, the load was Reloader15 to typical .500 Jeffery load data, Woodleigh 535 grain, Federal 215 primers, and the usual foam backer rod.
There is 11” of snow here and it was 35°F/1.6°C so no shots at target and no chronograph, just standing on my own 2 hind legs in the snow and shooting at a 1’x2’ rock about 30 yards away. Without the chrongraph I can only estimate velocity as ~2200’/sec. Needless to say, the rock absorbed 5 shots and didn’t walk away.......
Recoil was not bad, as expected a bit more than my .470, I doubt I will ever try shooting it off any bench other than a standing bench rest.

More to report once the snow clears and it warms up a bit.
- Mike