Underwood's 220gr Hard Cast is the heaviest commercially loaded 10mm Auto round available. At 1,200 fps, it generates 704 ft-lbs of muzzle energy and carries more momentum than any other 10mm load on the market. The extra 20 grains over the 200gr version means deeper penetration through dense tissue and heavy bone. This is a maximum-penetration load designed for the largest animals you might encounter in North American backcountry.

The 220gr weight pushes 10mm into territory that overlaps with moderate .41 Magnum loads. For bear defense, the combination of energy and bullet weight gives the best possible chance of reaching vitals through a frontal skull or shoulder shot on a charging animal. The hard cast flat-nose profile cuts a full-diameter wound channel without relying on expansion. It will exit most medium-sized game entirely, which is the intended behavior for a penetration-focused load.

This load recoils hard. The 220gr bullet at 1,200 fps from a semi-automatic generates a slow, heavy push that is different from the sharp snap of lighter, faster 10mm loads. Shooters need to practice with it regularly to maintain accuracy under the recoil impulse. The extra weight also affects feeding in some pistols. Glock 20 and EAA Witness models generally handle 220gr loads without issue, but shorter-barreled 10mm pistols may need a stiffer recoil spring. Test thoroughly before carrying.