Stan,
I get a 50 -75 fps increase, depending upon the load, in my .475 83's when going from 7 1/2" to 9". I don't have any 500WE's with barrels longer than 6", but I would expect an increase on the same order of magnitude with that cartridge. Not much, in other words. The pressure with both cartridges doesn't lend itself to dramatic increases with extra length.
I suspect that most people, after they use one a while, may consider revolver barrels over 7 1/2" to be a bit unwieldy in the field. I use 2 9" 83s ( the other's a .357), and used 10 1/2" SBH's for many years in IHMSA competition, but field use while hunting is different than range work.
In fact, I must say that after 45 years or so of considering 7 1/2" PERFECT in single actions, I began to prefer 6" 83's to anything else a few years ago.
Since this is you I'm talking to, I guess I'd better say "...no, none of my 7 1/2's are for sale...", but still, I'm thinking that a little bit shorter is a little bit better. Certainly not much need for longer around my house.
