Anyone ever play with the .50 Whisper by J.D. Jones / SSK, ind.? If so, what are some of the loads you came up with? And how powerful is it?

Not to split hairs, the the Whisper round that JD makes is the .510 Whisper.
According to their site, it launces a 750 gr. bullet at 1050 fps. I am sure SSK can supply reloading data for the .510 Whisper if you buy a barrel/gun from them.

SSK makes both the .510 & .500 Whisper. The .510 is a little more tricky to make and I think it was made for the military. I also think it is mainly for sub sonic loads, where as the .500 W. can be loaded both sub & hot.

The round that has 90% of the energy of the .50 BMG is not the Whisper round, but the .50 Peacekeeper. http://www.sskindustries.com/atlantis/cartridges.html

I stand corrected, the .50 Whisper used the .460 Weatherby case with the belted head, whereas the .510 Whisper has no belt. The .50 Peacekeeper is a long cartridge, very long in fact, whereas the two Whispers are quite short and stubby.

We seem to be up to 3 different rounds here. The .50 that has 90% (88% really) of a .50 BMG is the .50 Peacekeeper, also made by SSK. The 2 Whisper's are the .510 which is made from a .338 Lapua brass, and the .500 Whisper that is made from the .460 Weatherby brass, which I'm interested in. It is capable of moa accuracy at 600 yards, and can use heads from aprox. 500 gr. to over 900 gr., although the 750 gr. Hornady A-MAX seems to be a very good one to use. If your not familiar with any of the Whisper series from J. D. Jones / SSK you owe it to yourself to check them out! All Whisper rounds must be capable of extreme accuracy and be able to be loaded subsonic and hot. (And by the way, they are all out of short barrels to, 16" - 18") Although there are many different ones, the most popular are the 300, 338, and .500 Whisper's. (The .300 & .338 are outstanding!)
So, back to my original question, does anyone out there have any real life experience with the .500 Whisper?