In the early 70's, I tested these BRI slugs in an Ithaca Deerslayer smoothbore which was quite accurate with Remington Foster-type slugs, 3"-4" at 100 yards. There were very few rifled shotgun barrels at that time, and BRI claimed these slugs could be used in smoothbores. These slugs were .50 cal., and housed in a two-piece plastic discarding sabot, much like the fin-stabilized, long-rod penetrator armor-piercing projectiles used in tank guns.

These BRI's would not shoot from mysmoothbore, some even breaking in half, and making two lopsided holes in the target (50 yds). A couple hit point-on, most hit sideways, and two or three broke in half through the waist section.

This was BEFORE the makers announced that the bores had to be rifled. They were supposed to fly point-on from a smooth bore because they were "shaped like a dart" with a plastic plug in the hollow rear section-allegedly "fin-stabilized". Obviously, this idea did not work at all. Subsequently, they decided that a rifled barrel was necessary to shoot them. Then Winchester bought the design, and I guess they still make them (but the ones I tested were in a white & blue box labelled "Smith & Wesson - BRI"!!

(If you take a look in the old, original Lyman Black Powder Handbook, they shot some of these slugs from a .75 cal. smoothbore Brown Bess flintlock musket using black powder. Darned if the Bess didn't shoot them better than my Deerslayer!!)