Yep, the .204 will kill a deer, you can also pound a nail with a screw driver but it does tell somthing about ones I.Q. if they do so. Use the proper tool for the job and for deer hunting the .204 is not the right tool. I run into lots of people who want to see what is the smallest caliber they can use to kill deer. I think it is an ego problem. Lets look at this from a different view for a second. If you had to hunt from the ground, no tree stands, and deer had fangs and claws, and getting wounded tended to really piss them off and made them want to eat you, would you still want to use something like a .204? If a person is a conscious hunter then they use a cartridge which will ensure a clean kill and give a reasonable margin for error if things do not work out quite right.