it is not a good idea to shoot deer with FMJ bullets, nor is ethical!!!Don't try to out shoot your ability / shot placement is the key! bullet weight ? any weight that your rifle shoots best! a 22lr will drop any deer, 223 / 5.56 is traveling at Mach 3 has a big advantage. I have taken four over the years one with a AR-180 the other three with colts. all with FMJ