Not a lot of posts lately, so I thought I'd stir the pot. I have a FA M555 (6"), originally in .50AE, but now also sporting a .500WE cylinder fitted by FA. I've had the gun for about 15 years, and the .500WE cyliner for about 4 years, and have handloaded extensively for it. I thought I'd share some thoughts.
I very much like the idea of having the dual cylinder gun. .50AE brass is plentiful and relatively cheap; factory ammo is easy to find. Factory ammo is not wimpy either; for example, I've gotten Speer 325gr Gold Dot HP factory load to clock 1493fps. I've also read reports that this bullet really stands up well on large game. I use the .50AE brass for most of my light loads, and reserve the more expensive .500WE brass for heavier loads. If you get a chance to own a dual cylinder 50cal, go for it.
The .50AE is a bit of a challenge to load hot, because of the taper crimp limitation. However, I've pretty much solved that problem in my gun. My favorite bullet is a custom LBT cast from a mold Veral Smith made for me. It casts a 415gr LFN that is designed to maximize powder capacity, and take up most of the usable space in the cylinder without protruding. I seat the bullets with no crimp, but with the crimp just beginning to touch the case. Then I back out the seating stem, and lower the die to crimp. I lower it exactly .125 inch; I achieve the exact dimension by removing a .125 spacer (I think from Redding), leaving the die lock ring in place. This exerts a very heavy taper crimp, but with the close tolerances of the FA cylinder, it still headspaces reliably. I've been able to get 1270fps with this bullet without "bullet creep". I test by having a single cartridge stay in the cylinder thru 8 (ie, 2 cylinder fulls) firings. If it survives without significant creep, I consider it good to go.
I've used this technique to get 1378fps with a commercially cast 380gr LBT LFN, and over 1500fps with the Barnes X 275gr HP Bullet. Unfortunately, that last bullet, as well as my custom cast bullets, won't work in the .500WE case, because the noses are too long for the cylinder. And as I said, I've pretty much stopped pushing the envelope in the .50AE cases now that I have the .500WE cylinder; I use the .50AE cases for mid-range and light loads. I know I could trim the .500WE cases to accomodate long nosed bullets, but just don't see the need.
My favorite bullet in the .500WE is the Cast Performance 440gr LBT. I can easily push it to 1250fps; it could do more, but recoil gets to be more than I care for. I can push the commercially cast 380gr LBT LFN over 1270fps, and again, recoil is my limiting factor. I've gotten over 1370fps with the Hornady 350gr JHP XTP Bullet; recoil as well as FA's recommendations are the limiting factors. With the advent of the .500 S&W Mag, .500 diameter bullets are now really easy to get. Most will work fine in either the .50AE or the .500WE, at least in a revolver.
My top end loads use WW296 powder. I also use AA#9 for slightly reduced, but still heavy loads. For mid-range loads, I use AA#7, and use AA#5 for really light loads. I find loads using cast bullets from 340 up to 440grs, moving out at around 1000 to 1100fps to be fairly comfortable to shoot. When they're moving at around 700 to 900fps, they're downright fun. And what more could be said about Freedom Arms quality? By the way, my M555 "field grade" originally had the rubber grips; when I first bought it new, I ordered unfinished grips from FA, and had them professionally fitted by a retired stock maker. They came out great.
If you own a .22LR rifle, a 9mm or .45Auto pistol, a .30-30 rifle, and a 12ga shotgun, you probably don't need another gun. But don't ever tell your wife. The beauty of living in America is you're free to own more, and a Freedom Arms revolver in .500WE ought to be on your wish list if not already in your gun safe.