Congratulations on your Spike Bull!!! That'll make for many nice meals this winter. It seems that 16" is the magic number for that .264, but I'm pretty sure that with a Barnes the penetration would be much more. Regardless, that bullet certainly rattled the clockwork of your bull, no doubt about that. The retained weight of your bullet is a bit less than what I get with the Nosler Accubond which seems to retain around 60% of it's weight; at least it did so with my Boar at 85 yards and my Pronghorn at 300 yards.