Brenneke slugs

[Taz77]

At the last Cow Palace gun show, I saw some of the Brenneke K.O. slugs, and on the box, it says it'll work with smooth bore barrels and rifled barrels. I've read that sabot slugs are terribly inaccurate in smooth barrels, and rifled slugs leaves a plastic residue in rifled barrels as well as not be accurate.
I've also read on other forums that Brenneke slugs are pretty accurate.

What makes the Brenneke slugs work well with both type of barrels and still get pretty decent accuracy?

If they really work that well, and very nicely priced, I may be tempted to get a few to blow up some bottles at Los Altos...

[shecky]

Brenneke slugs have a wad of some type connected to the rear of the actual slug. In a rifled barrel, the wad engages the rifling, imparting stabilizing spin. I believe the actual slug on K.O.s are rifled, which allow the slug to pass through a choke without adverse effects. Fired from a smooth barrel, the wad simply acts as drag, keeping the slug facing nose forward all the time, kind of the same way fletching would work on a dart.

Some rifled slugs may leave residue, either plastic or lead, depending on the design, in rifled barrels. I suppose sabots can also do this. Sabots are specifically designed to engage rifling in a barrel. Fired from a smoothbore, the bullet in the sabot gets no stabilizing spin, nor does it usually have a inherently stable design like a Foster or Brenneke slug. You can probably expect a sabot bullet to tumble about unpredictably shorty after leaving the barrel.