I can tell you from personal expierence that a 5.56 will not go through and engine block. I know i have tried in combat. I will also tell you yes they will kill a moose. I have seen Caribou taken with a .223 and they were shot a few times in the lungs and they laid down after a bit and died. Moose can be killed with one as well. Moose tend to lay down soon after being hit so if you can shoot it a few times in teh lungs it will work. That being said there is now way in hell i would ever use on on even deer. The guys i saw do it were inuits and the ammo is cheap and plentiful and they are outstanding hunters. They would shoot the Moose and then stop for an hour or so and then go find the Moose. Never went to far but they were 50yrds away when shot and shot several times. you can kill a man with a bb gun but that does not mean it is an effective weapon