The Taofledermaus crew of merry shotgunners found surprising success with a .70 caliber polycarbonate round with a carbide penetrator against hard plate armor.
The armor used, Level III plate from AR500, held up to a .308 round like a champ but the polycarbonate shotgun slug acted like a sabot for the 1/4-inch carbide core which, propelled by re-purposed Federal low brass, went through the plate like a fat kid through cake.
Source Article from http://www.guns.com/2015/11/30/carbide-polycarb-slugs-vs-ar500-armor-video/
