"Change is slow. Marine Corps senior leaders have always had an extreme fondness for anything that can double as a club for beating the enemy to death."
Perhaps. However, there is also this comment which I believe to be on point: "I don't see any disadvantage -- the M-16A4 is a good weapon and in open combat in Afghanistan been proven better than the kiddy M-4 in open area combat." I suppose if you think we will ALWAYS be fighting in cities . . .
Also for the traditionalists: The U.S. Marine Corps is sticking with its Vietnam-era, M40 sniper rifle series, despite complaints from scout snipers who say they need the modern, longer-range weapons used by special-ops snipers. Marine scout snipers are considered to be among the best snipers in the world, but many are frustrated at the limitations of the current M40A5 sniper rifle. The A5 is based on the Remington M700 short-action design that's chambered for 7.62x51mm NATO, like the original M40 Marines used in Vietnam.