P2P Core Defense Powder Balls .68 Caliber 100 PackP2P Core Defense Powder Balls . 68 Caliber 100 Pack P2P Core Defense has revolutionized less lethal . 68 caliber self defense. This patented Core Defense product is a . 68 caliber round featuring a patented outer shell that houses a perfectly centered steel ball encased in a layer of inert powder. The result is the hardest hitting, most accurate inert defense round on the market. Prepared 2 Protect Core Defense . 68 caliber ammo is compatible with