H&R (A Remington company) have produced a new shotgun designed specifically for slugs. H&R Pardner Pump Slug features a proprietary rifling design called Ultragon which was designed to provide greater slug accuracy. From the press release:

Rifling further enhances the accuracy potential of the Pardner Pump Cantilever Slug Gun. Ultragon is a proprietary rifling design comprised of six lands and grooves without sharp edges like traditional rifling. This design imparts bullet spin without leaving sharp impressions on the sabot jacket or foster-style lead slug. The result is a better gas seal and less loss of pressure, which equals higher velocity and better accuracy

Specs:

Model: Pardner Pump Slug (NP1-12C/NP1-2SC)
Gauge: 12 (2 3/4 and 3-inch)
Stock: American Walnut / Black Synthetic.
Barrel: 22 inches. Ultragon rifling.
Metal Finish: Blued
Sights: Cantilever Scope Mount
Length: 42 1/8 inches
Length of Pull: 14 1/2 inches
Weight: 7 1/2 lbs.