It's tough to recover bullets that go all the way through and every one did, including the one that broke the onside shoulder going in and exited the far rib cage at 314 yds.. That was a handloaded 150 gr. rn core-lokt sitting on top of 33 gr's. of IMR 3031. That one made it all of maybe 40 yds. before it folded up. The fact is, you ain't got a clue how little it actually takes to kill a deer with a shot through the lung cavity so here's one for you. I've killed several with 40 gr. .22 WMR hp's through the lungs at 25-75 yds. and none went so far as 100 yds. after the shot. I also killed a couple with 38 gr. HP's from a 5mm Remington magnum rimfire. One forkhorn buck shot through the shoulder blade from 60 yds. and damned if the little bullet didn't exit !
I don't doubt that one can kill deer with a .22 rimfire through the lungs. There are thousands upon thousands of humans who have died from .223 FMJ bullets over the past 50 years, so an expanding bullet is certainly not required to kill a medium sized mammal, but accepted practice for hunting deer-sized game in most of the civilized world over the past several decades is to use expanding bullets within a range that will result in expansion. Of course mileage varies.
