Mavin- your WW are softer about 1/2 weight difference compared to the ones I have that were collected 20 years ago.
CB- your .50 has a "Gun Maker's" barrel on it, I think, which is square bottomed and probably .010" TO .012" deep. The .490" should be fine, with a .020" patch, BUT- you'll have to try it with an actual hunting-type load. My WW would run 10gr. lighter adn maybe .001 larger- maybe. .50 is pretty small to start with. And yes, I know a .50 cal. pistol with 50gr. charge will kill a moose - that's getting back into tricks rather than good managment, though imho. Try 115gr. to 120gr. 2F and let me know how it works - patch appearance - bet it's OK and so's the accuracy. Oh - I'll give you some .020" patch material. Your .020" runs .016"/.017 in my measuring tools and I'm sure that won't cut it- well, actually it might just cut - won't seal, though imho.
Call.