content: Using a sub-caliber round like that let's the operator take out smaller targets. People, soft-skinned vehicles. .50's are considered anti-material rounds but are also useful for sniping. The regular round for that is about 2.25 inches in diameter and cane in several varieties. This page has a nice overview: http://world.guns.ru/grenade/usa/m1-recoilless-rifle-e.html