US military's love/hate relationship w/ combat rifle

cartridges.

Stumbled onto an article, within an article, regarding alternate choices in combat rifle chamberings the US military has considered over the last 40-50 years. The next change over 5.56 NATO (223R) was the focus. Alternatives included offerings from 6mm all the way back to 7.62.

The 6x45mm caught my eye, due to the fact that it would seem to be a simple fix: 6mm expansion nipple of the 6x45mm sizing die with one pull on a 5.56 (223R) case makes the change. Go with a 75-87gr. projectile, easily an upgrade and AR compatible using 5.56 brass, with lots of bullet choices. The changeover would be less expensive with an increase in downrange performance in effective range, trajectory and wind drift.

I can see the added expense of 6.5, 6.8 & 7.62, but in my USMC experience carrying the M16/5.56, anything would be an improvement. Never created confidence as a combat/battle weapon, a major topic of conversation among active duty personnel, especially special service types.