A lot of deer hunters put a rifled barrels on their shotgun and shoot sabot slugs. I know that without rifling a sabot slug has no stability.
But there are two common types of slugs designed for smooth bores:
- Brenneke (a.k.a. European) slugs are cast with spiral grooves that supposedly impart some spin from aerodynamic forces once the slug is out of the barrel.
- Foster (a.k.a. American) slugs are cast with hollow and/or finned bases to maintain stability in flight (due to the center of mass being in the front to prevent upset).
I've shot both kinds out of an unchoked barrel and been less than impressed with their precision: From a bench rest I don't think I've seen extreme spread less than a foot at 100 yards. But I have no idea whether this is actually bad or if that is the limit of precision on a smoothbore.
So what is the best accuracy I should expect from shotgun slugs in a smooth barrel, shooting from a bench?