Does your state have a minimum barrel length for handgun hunting? If not, then the choice is yours. With the power in a .500 S&W mag, I doubt that the little bit of lost velocity of a 4'' barrel is gonna make much of a difference. What will be obvious tho is the increase in amount of felt recoil. The term ''half-lug'' just means the lower part of the barrel(in which the extractor rod sits in) only goes halfway, as opposed to a full lug barrel, which extends out to the end of the barrel. Some folks prefer one to the other mainly on aesthetics and balance. Full lug barrels sometimes help with felt recoil and barrel rise because they add weight to the gun and put more weight forward.

I have a standard 4” (3” with 1” comp) and a 5” John Ross Special (half lug and no comp). Both weigh about 57 oz. Either would make a good carry gun in very bad neighborhoods where bears could be an issue, but both are too short where I live to hunt with. Where I live 6” barrel is minimum, so my 6 ˝” PC Hunter would be appropriate, but wouldn’t make a good carry gun at 70 oz. without a scope.

I have shot the 4" 500 S&W and also the 2 3/4" 500 S&W. I own the 2 3/4". Velocity loss will not be an issue.

The 4" will be plenty accurate with practice as is the case with any firearm. My 2 3/4" was at first a monster to shoot but with practice and changing my grip I am reasonably accurate at short range - 20 yds with no rests.

I carry mine while hiking in mountain lion and bear country; and love shooting it at the range!