Cor-Bon originally developed three loads for the 500S&W, in 275, 400, and 440 grain. I believe the 440 ran the highest pressure at 50ksi. Comparing the specs of the currently offered 440gr load to those offered in the beginning shows no difference in performance, so there has been no downloading for the 500S&W. I'll have to check on the 460.The ammunition manufactureres have universally down-loaded both the .460 and .500 S&W cartridges to the realm of 50,000 to 52,000 psi, in order to facilitate extraction from double-action revolvers.
All the reloading data I'm aware of also takes that into consideration.
Check Hodgdon's site, it shows multiple loads above your 50-52ksi limit, with one running 57.3ksi:
http://data.hodgdon.com/cartridge_load.asp
Maybe I just got lucky, but my chambers have a mirror finish. I can't really say much about chamber dimensions without the proper equipment other than I don't have any problems. My experience with bad chambers is limited to another manufacturer but that is another discussion.I'm saying that production S&W chambers leave a bit to be desired, as to size & finish, in both calibers. Compared to Freedom Arms' chambers, they look like pipe joints or plumbing fixtures...
Well there's your problem right there - trying to put six cartridges in a five round revolver!Multiply that by SIX, and you have sticky extraction, sure as death & taxes...