I never carried a BAR, but I figure that the pig must have been worse because the BAR had a magazine while the M60 had that belt of ammo which was always pushing into you as you carried it (or spilling all over). Not a bad gun at all (when it wasn't totally worn out) but not fun to carry.
As for the High Standard riot gun, I luckily never found one. But it sure did look like an awesome weapon in the movie.