My ranking:
#1 - M1 Garand
#2 - M14/M1A
#3 - 1903 Springfield
In my extremely biased opinion, anything smaller than a . 30 caliber is a JOKE for a battle rifle. Why do I have this opinion? Well, as a life long hunter, and having used . 30 and . 22 caliber rifles to kill a variety of game, even though yes, a . 223 will kill a human, it is also much less likely to do so for a given point of impact than a . 30 bullet. When I was in Basic Training in the mid 1980's, the two lame reasons our weapons instructors gave for the US Military switching from the . 30 to . 223 caliber, was the lighter ammo meant a soldier could carry more, and it was felt preferable to wound an enemy ratrher than kill him outright, as it would then require additional enemy personnel to carry the wounded soldier off the battlefield, thereby taking more than just the one enemy "out of action".
I absolutely disagree with these ideas for the following reasons:
Simply by carrying more ammo means nothing. As anyone who has ever served in the US military can vouch for, the large majority (in the last 50 years I'm certain) of draftees and enlistees have never seen a gun, much less have any experience firing one. By telling them they can now carry twice as much ammo as before, they easily get the idea "hey, I have all the ammo in the world, so I can just spray lead and don't have to aim". As most any kid who was fortunate enough to grow up learning how to hunt can tell you, proper aiming and conservation of ammo will benefit you much more than just mindless spraying of lead and hoping the odds end up that you eventually hit something.
While it is true that some military forces would simply abandoned their dead on the battlefield, many will also carry their dead off the field. Which negates the idea that wounding an enemy takes more of them out of action. Also, a wounded enemy can eventually return to battle, and someday, he might kill me! But if I kill him the first time, gauranteed he ain't ever going to be a threat again.
One final thought: Carlos Hathcock, one of, if not the most famous US Sniper in history, said he felt the absolute perfect and best suited round for killing a human being was some type of . 30 caliber. To me, someone with 93 confirmed kills as a sniper, many at ranges beyond 1000 yards, is the best authority on such a subject.
Sorry for the long winded rant, but as you can tell, I am quite biased and opinionated where firearms are concerned
Tom