Without going through the whole story behind the development of the 5.56mm. I will continue.
Its all about twist rates and the round itself. Back during testing of the 55grn bullet it was used in the first AR-15 using a twist rate of 1 and 14". It was very unstable round back then,but if it were to hit you it would really tear up flesh and internal organs. So Eugene and the Army cut it off. The next twist rate was 1 and 12". This is where the round really had some significant accuracy and on top of this, it went in the body through a small hole and it zigzagged throughout the body doing an amasing amount of internal damage. Did I say it was accurate too? So much so that the rifle went almost straight into Competition throughout the services. Oh, by the way the 55grn round had a good range of 450-500 yards. The Air Force picked her up immediately.
Now, this why the 5.56mm and the 55.grn round were coupled together and did it's part in Vietnam. Now this was after the "Jaming" problem in the mid 60's.
Anyhow they would find dead NVA and VC that looked like they were not hit. They found very small holes going in to the body and then would find huge explosive of a wound that came out the other side. For instance the round would hit someone in the chest and come out there around the upper thigh region. The 55grn round would start to yaw if it hit anything denser than air.
This is why we either go back to the M16A1 or we go back to a M-14, DSA with collapsable stock and a 18-20" barrel or even the SLR. We all know that the T-48 and the T-44 trials were rigged, and evebn the U.S. Army stated loudly that if it wasn't made in the US then it doesn't belong here! I am a big fan of the SLR because I own one.
Bottom line, the 5.56mm would be a good choice in Irag and Afghanistan as long as they used the the 1 and 12" barrel and the M16A1 platform.
On the other hand, the 7.62mm round is being tested again right now in Afghanistan by SF and certain other identities. Their rifles are made by DSA, mostly at this time. I know for a fact that they all are impressed with it.
The 62grn round was developed to give the rifle more range and extreme accuracy. Problem is is that it does not expand most of the time when it hits anything denser than air. The rounds are simply going through people over there and there is hardly any hydrostatic shock happening to the body. Going up in round weight is not the answer with the 5.56mm round. The 7.62mm is the way to go now! This comes griefly as I am a huge fan of the M16A1 and the 55grn round and full auto for the instances of being over runned or on the assualt. This brings up another part of doctrine on the USA. If you have an AK47, what is the first part of the selector, right off of safe are you putting it on. Figure that one out and you will have guessed were the Warsaw Pact nations were coming from. Now, what is the first position the selector goes to after safe on the M16A1's and A2's. It is just as bad shite to keep using an arm that is using a 62grn round inside a 1 and 7" twist rate, especially if the rifle your using is an M4 series.
Just my $.002 worth of edumecation.
I hope that I have put the same aspect on this serious problem.