Better than M4, but you can’t have it

[Dominique R. Poirier]

“Two thoughts: 1) In the 7.62 v. 5.56 debate a round in the 6.5 - 6.8 range would have been a good common sense compromise; 2) It still probably isn't worth changing, and that includes the rifle as well as the round. Just keep what we have unless something revolutionary can be fielded.”

The main reasons justifying the evolution toward the 223 ammo were that combat ranges had significantly shortened from WWII on and that a man could carry about 180 rounds of .223 instead of an average of 60 to 90 maxi with bigger ammunitions such as 8mm and .308. The Germans understood that first and invented the first assault rifle (the Sturmgewehr MP 43, and MP 44) firing a shortened version of the 8mm Mauser with a case's length reduced to 33mm instead of the 57mm of the classic 8mm Mauser. This gun and its ammunition seems to have inspired Mikhail Kalashnikov.

Long range shootings are now traditionally left to snipers who are trained to shoot at distances superior to 200-300 yards with .308 ammo and bigger. The classic .223 begins to loose significantly in accuracy beyond 200-250 yards whereas the reasonable limit with .308 is in the surroundings of 600 yards.

“What would be revolutionary? I don't know, but a couple of things come to mind: caseless ammo (….)”

Caseless ammos have been the object of serious experiments in Germany with HK experimental assault rifles during the late 70’s; but some problems, such as spontaneous auto-ignition, were never totally solved. Thus, HK gave up this project.

“(….) as well as railguns and coilguns. I have no idea if any of these can be made reliable and infantry proof in a shoulder fired weapon. The experiments that are going on now with railguns and coilguns seem to be with larger weapons such as naval guns.”

From recollection an electromagnetic pistol has been made in United States during the late 60’s or 70’s I believe but the performances and technical constraints of this experimental gun proved to be unsatisfactorily.

“I don't know why caseless ammo (how about a 6.5 or 6.8 caseless?) hasn't been pursued.”

6.5 and 6.8 rounds get us back to the problem of the number of ammunition a soldier can carry. During WWII Italians and Japanese soldiers used 6.5 ammunition whose cases’ length were superior to 50mm and whose case diameter at the bottom were similar to this of a .308, 8mm Mauser or 30-06 U.S. See the ballistic performances of modern civilian .243 to .270 Winchester for comparison.
Hard to make this diameter’s case smaller as the Soviets experienced it with the 7.62 X 39 Kalashnikov. The finally opted for a 5.56 X 39 circa 1974 (Kalashnikov AKS 74).
Remember also that the WWII .30 M1 ammo (7.62 X 33mm for U.S. M1 and M2 carbines) whose diameter at the case’s bottom is smaller and close to this of a 32 ACP proved to be unsatisfactorily owing to its poor ballistic performances and power.