No, the gun Legionnaire just put up a link to a thread on is something else, a 600 Nitro Express made in Europe somewhere. That gun is definately commercially available if you're psycho enough and have $3k+ laying around...and will wait for one to be hand-made.
But THIS thing is a 50BMG, or at least made up to look like one.
I for one don't think it's photoshopped. First, too many of the details are right - there's a three-screw mechanism clearly borrowed off the SAA, the cylinder pin is exactly the kind of "bigger hammer engineering" you'd expect, the proportions are dead on between the picture of it being held versus laying on the pallet, and most of all, there's the hammer spur, grip and trigger position, which are all correct for (large) human-sized hands.
Now, whether or not it will FIRE is another matter, it may be a fake all the way. But I don't think so.
Look closer. First, the bluing has "brown highlights". You get that on some old-school bluing methods on plain ol' steel, but NOT on black anodized aluminum - which would otherwise be a LOT cheaper to machine if this was a big mockup.
Second, look at the woman holding the gun in the second pic. Her shoulders aren't at the same height - I think she's struggling to get the barrel up and horizontal for that shot, which makes sense as that hand being centered more on the gun, is holding up more weight. Look at the knuckles and hand position on the right hand - am I crazy, or is she white-knuckling that grip? If it's real, it weighs somewhere around 20 - 30 pounds I suspect...15 *minimum)
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Third, look at the work that was apparantly done at the rear sight. Looks to me like it was meant to be fired.
I can't swear to it, but I think at least ONE of those may be either a fully functional specimen, or was at least planned to be.
Whoa!