I have a friend that was asking me about the 300 whisper round the other day and I couln't answer his question. What he wanted to know was how much killing power could he get out of the sub-sonic whisper? I assume it would be enough to kill a coyote (that's what I told him anyway). But he wanted to know if it has enough power to kill deer. I told him I was sure it's not recomended for deer, but didn't know for sure what kind of power he could get out of it. How about it? I assume it would kill a deer with a head shot, but how about a shot to the vitals? Just curious. He has ordered an AR-15 upper in the caliber which he plans on putting a silencer on. If nothing else, it should be a fun paper and rockchuck shooter.