I too own and shoot a couple of Webleys. An 1886 marked MK I and a 1914 MKIII. The early one with the brids head grip and the later with a rounded backstrap grip. Both 4 inch barrels and both had been ground for .45 ACP. The MK 1had a broken latch spring when I first aquired it. I believe from shooting full power .45 acps. A testiment to the strength of the war horse made for BP loads originally.
I only shoot my hand loads in them to duplicate the .455 /.476 load. I use the Remington .45 Colt HB swaged 255 gr bullets and get good accuracy. The brass is mostly .45 auto rim, but also ACP brass with full moon clips. I use the .455 lee dies to have the proper shape and handle the large diameter bullets.
Both revolvers were in otherwise very good condition. The MKIII looks to have been re-built and remarked and proofed at some time.
I like having the Rifle and side arm of the same origin and era. A little odd, but fun.
I have a very nice Enfield MK2 (not altered) with the hammer spur and single / double action. About minty. Fun revolver also to go with the SMLE Mk4s.
I will bring one of the early Webleys on my next boar hunt, along with the Martini .375 Express.