I shot 2 and reloaded for one of them( 225 grains of powder, if memory serves!!).
One was a McMillan that was not too bad, other than the muzzle blast it was alright to shoot. It weighed better than 40 pounds ready to go( I think).
The other was a bolt gun with a muzzle break( the real reason my memory is shaky is due to firing this unit). It weighed well under 20 pounds on the line. I think the barrel was a lot shorter than the McMillan too. I shot it twice..... With whimpy 660 grain bullet loads..... I would rather get in a streetfight with Mike Tyson than do that again.
On the second shot I realized that burning smell was from the blast out of the brake has actually burnt some of the carpet on top of the shooting bench!
I have fired a 505 Gibbs that weighed 10 pounds that was loaded quite hot. It was heavy in recoil, but managable. The lightweight .50 was not.
Fun to talk about. And rather forgiving to reload for( in my limited experience).
The biggest downside to owning one would be everyone would want to talk to you at the range, so load development would take about 10 times what it should. But at 800 yards, when them sissy .300 mags are getting tossed around in the breeze, they are the shizzle.
Mark and the bag of shot between me and the gun on the next shot dog.