S&W has applied to SAAMI for 60,000 psi on a strain gauge as the acceptable max pressure for the .500 S&W. This correlates to about 50,000 CUP using the near-obsolete "copper crusher" system of measurement.
The .454 Casull runs about 5,000 psi higher pressure than the .500, and Rossi makes a stainless M92 clone in that caliber that works well. I think a .500 carbine is doable, but not just on any old levergun made out of any material.
The .500 S&W at full throttle is in a whole 'nother league from any other repeating handgun when it comes to power. With big flatnose 510 grain cast bullets with long noses and short shanks, I have come within 100 fps of some 510 grain .458 Winchester factory loads out of a rifle(!) (.458 factory ammo has been downloaded over the years in deference to the German and Austrian makers who persist in chambering break-open double guns in this caliber.)
The .500 in an 8 3/8" handgun with top loads is the equal of the 450 Alaskan lever action rifle.
Whoever makes a .500 rifle better make sure it will take a loaded round length of 2.320" or my revolvers will be more powerful.
As to wildcatting, in a handgun, bottleneck rounds generally have problems. In a rifle, .50 Alaskan brass is bigger, as are a number of other cases. .22 and 6mm WSM cases are very similar to .500 S&W. I'd like to see the case shortened to 1.000" and put in a five-shot Redhawk, a .500 Special, but I'd probably shoot it once and go back to the full length case.
You would not *believe* the improvement in balance with my de-lugged and de-comped .500 at 63 ounces. Recoil not enough different to matter.
http://www.john-ross.net/images/Cust500.jpg
Next step is a de-lugged 5" gun. Should go about 58 ounces and sling a 510 at 1600 or a 725 at 1050.
I would shoot a Scandium .500 with a 6" barrel if it had a regular stainless cylinder.
JR