460 Rowland in N Frame

[Arisin Wind]

I was reading some articles about the 460 Rowland and how gunsmiths convert S&W 625s, 25s and Ruger Blackhawks to this super 45 ACP cartridge. Apparently the 460 Rowland operates at around 40,000 CUP. This seems way too high for a 45 caliber cylinder in a S&W to handle - and maybe even a Ruger 45 cylinder. Is this a safe conversion? If so, why can't 45 Colt S&W 625s and 25s be loaded to 40,000 CUP?

Something just doesn't seem right.