I've never shot a deer with No. Four Buck but have shot a bunch of coyotes with it. I've had a few experiences that have made me question its penetration ability on bigger stuff. Interestingly enough the FBI used No. Four Buck as their issue shotgun load back in the early 80's. Eventually the move went back to bigger buckshot. Currently a lot of attention is being focused on #1 Buck. #1 Buck has been "re-discovered" in LE circles, in large part because hunters here and abroad have made good use of its unique combination of size, mass and pellet count. I ran across an article written by Peter Hathaway Capstick extolling the virtues of #1 Buck way back in the 70's. It was used extensively in South America for Jaguars and in Africa for Leopards. There are lots of good options in today's market.