You'll get many opinions, but I'll start it off. First, I didn't know they made a .277 SST in 120 gr, but I know you can get 130 grainers. Use that bullet and shoot em in the lungs. They won't go far. Or use the 130 gr Nosler BT, as I do. Truth is that any hunting bullet should do fine, but the SST and BT will shatter the lungs very well. Messy but effective.