Rifled Slugs Aren’t Really Rifled

The rifled slugs you see here were among several I recently tested against Dave’s Ballistic Buffalo for an upcoming column in the magazine. One, obviously, is unfired, the other was recovered from the depths of the buffalo after I fired it out of a smoothbore 870 fifty yards away. I show them here not to talk about terminal slug performance (that’s the topic of the column) but to illustrate how “rifling” on slugs really works.

“Rifled” slugs, also called Foster slugs after their inventor, Karl Foster, who came up with the idea in the 30s, aren’t really rifled. You can see the “rifling” on the unfired slug. On the fired slug, the vanes have been squashed flat, which is what is supposed to happen. Vanes do not make the slug spin. They may originally have been set at an angle in hopes of making the slug spin, or, more likely, in hopes of making hunters think they spin, but, what they really do is help the slug swage down through the choke.

Even with the vanes on the sides to help them squeeze out of the muzzle, Foster slugs and Full chokes don’t mix well. Skeet, Improved Cylinder and even Modified chokes all handle slugs fairly well, but once you go to a Full choke your groups will often grow from 3 or 4 inches to 7 or 8, I think because the slugs deform as they pass through the choke.

A lot of you have asked me what happens when you shoot Foster or rifled slugs through a rifled gun. So, I tried it. My Deerslayer III, which shoots sabots very accurately, sent Foster slugs all over the place at 100 yards into groups that were 6 to 8 inches across. And, they leaded up its barrel, too.

I can’t see any reason to shoot Fosters through a rifled gun, especially when there are some excellent attached wad, fullbore slugs available that do shoot well through rifled guns, among them, Remington Buckhammers, Lightfields, Brenneke K.O.s and Winchester Rackmasters. The Brenneke K.O.s cost about the same as Foster slugs, and most other full-bore, attached wad-type slugs cost far less than expensive sabots.