BT's are designed for high ballistic coef. for flat shooting. They get a little less penetration than a spiral point would. As far as expansion, depends on the design. Lots of different ones do lots of different stuff. For small deer at close ranges up to 200 yards, I think the bullistic tips from nosler are the ticket. For real big deer and mulies, the scirroco's, for moose and bear, the Partitions, A-Frames. Just do the homework. I haven't tried but hear the SST's are good for small deer.