Obtaining a slug gun is easy: You can buy a complete gun or, if you own a popular pump or semiauto, there might be an accessory barrel available for your model at a lower price. But there are significant differences between smoothbore and rifled slug guns.
With a smoothbore gun (many are equipped with adjustable iron sights) firing Brenneke or Foster slugs at 100 yards are typical. When sighted in 2 inches high at 50 yards, they will be several inches low at 100 yards and then drop like a rock to about 10 inches low at 125 yards. Their effective deer hunting range is 100 yards at best.
These slugs can be fired in rifled barrels, but they will quickly foul the barrel with lead and destroy accuracy. They are best used in smoothbore guns. However, those 1-ounce, .70 caliber slugs, launched at 1,300–1,400 feet per second, make an effective close-range personal-protection gun in big bear country, and are widely used in that role by outdoorsmen and many wildlife biologists.
A sabot slug in a rifled barrel changes things considerably. For example, the Federal Vital Shok 12-gauge 3-inch Magnum Sabot Slug launches a 300-grain jacketed softpoint projectile at about 2,000 fps and, given that the rifling engages the sabot and applies spin stabilization to the projectile, is capable of 2-inch groups at 100 yards. When sighted in 3 inches high at 100 yards, it will be about on at 150 yards and around 7 inches low at 200 yards, with the power to harvest deer at 200 yards.