i'm thinking the angle was sharper than is appeared, letting it skitter along the ribs. still, it expanded, and stopped after only 3.5 inches. i'd send it to federal and ask 'em what happened. send the lot number from your box of ammo; even better, send the box and remaining rounds so they can be broken down and the powder weighed, etc. this could have happened with other rounds from that lot number. weird, truly weird ...