I still use them. The guys her use them. Mostly in their flintlocks...

http://www.americanlongrifles.com/american-longrifles-BBS-frame.htm I have used round balls, conicals of various weights, and sabotted bullets of various types. IMO, none of them kill any faster or deader than a patched found ball of the correct size. Perhaps some of the other type of ML projectiles have a range advantage. Hoever, a bullet with greater sectional density and inertia cannot be driven at as high a MV as a patched round ball. A round ball launched at 2200 FPS will show a flatter trajectory than a conical at 1500 over the first 100-125-yards. But the elongated bullet will catch up by 175-200 yards.