The best caliber for a battle rifle?

[extern]

Even more interesting, guys!
The 123 grain bullet of 6.5 mm Grendel ( pic: http://upload.wikimedia.org/wikipedia/commons/0/06/65G_144_123_129_120_90.jpg ) has the nose cavity for mass eccentricity generation JUST as the Russian main 5.45 mm bullet has! (pic: http://upload.wikimedia.org/wikipedia/commons/0/01/Cartridge_Kalashnikov_AK-74.svg )
What is this? Is this fortuitousness, coincidence or contingency?

 

[jmiln]

The 7.62 rd is probably the best choice for a battle rifle, especially for distances at 200m or more but for close range or in any type of urban enviroment the 5.56 is what id prefer. it lacks the stopping power of the 7.62
but the recoil of the weapon is generally alot less, compare the m-4 with the ak-47 and putting a series of accurate shots at the enemy is a lot easier with a weapon like the m-4 firing 5.56

 

[kato]

but the recoil of the weapon is generally alot less, compare the m-4 with the ak-47

The AK-47 (and most of those of its derivatives that are not of the AK-74 line) fires a comparably low-powered 7.62x39 cartridge, which is far closer in felt recoil effects to 5.56x45 than to 7.62x51 NATO.

 

[F-15 Eagle]

I think the U.S. and everyone else that uses the 5.56mm should just go back to the .308 or 30-06. That way there wont be any more complaints about stopping power. The 5.56mm is just way too small to be an effective rifle cartridge anymore.