I’m thinking it is the small diameter of the projectile rather than the force behind it that is the problem?
Mainly it’s the weight of the bullet. Heavier bullets are better, but there’s only so much you can do in a small caliber.
Exactly correct. It will pass through any part of a deer but a .22 cal doesn’t make a very big hole.
Normal 223 ammo uses a 55-grain bullet. They make 80-grain bullets for it but the rifle needs a faster twist barrel to stabilize it so as to have it shoot accurately, one in eight at least. M16 upper receivers with 1:8 twist barrels aren’t that had to come up with or at least they weren’t prior to a couple of months ago...