Yes the 223 is enough for deer ,although shot placement is critical. You must use a good game bullet and their arn't many choices here. My favorite ( my go to round) is the speer 70 gr simi sptr. ,it's constructed heavy enough to penetrate completely on a broad side lung shot,and will leave them plenty dead.Nosler makes the partition in a 60gr. but for me it isn't accurate enough. Sierra is making a gameking 65gr. for deer size game although extremely accurate as most sierra bullets are I've not tried them on game yet. I here lots of people saying sierra's don't hold together well on game but I'd have to dissagree, they have never let me down. Do understand that a 223 isn' going to leave much of a blood trail ,but is at least as humane as a broadhead, or moreso! Just pick your shot carefully or you'll end up wounding and loosing your deer. Bigger is better.