The Marine Corps Times reports that the long process to replace the M16 is nearing an end with "only a few signatures" remaining before the rifle is "relegated to a support role and removed from front line units." The Marines are modernizing its small-arms strategy, following on the heels of the Army which recently made a similar program change.
Maj. Anton Semelroth told the Marine Corps Times that, "The proposal to replace the M16A4 with the M4 in infantry battalions is currently under consideration at Marine Corps Headquarters."
The replacement carbine - the M4 - is a smaller variant of the stalwart M16. While the look of the two weapons are very similar, the M4 has a collapsible stock and a shorter barrel but the primary difference is weight and portability, two crucial considerations for an infantryman and as all Marines, past and present well know, "every Marine is an infantryman."
The M16 weights in at 8.5 pounds and the M4 is a full pound lighter at 7.5. The infantry has a saying: "ounces equal pounds, pounds equal pain:" an adage of great import for those who have toted a rifle in combat all day or night. The smaller size of the M4 also makes it better suited for close quarters combat and use inside vehicles or dwellings, two areas that are growing more important as urban warfare and counter-terrorism takes the front stage for combat deployments.
There is an off-setting drawback to the M4 - its shorter barrel means it is less accurate when targeting at the outside effective range of the rifle which is about 500 meters. Supporters of the M4 point out that this "drawback" must be understood in context. At 500 meters the 5.56mm round fired by both the M16 and the M4 are basically spent when it comes to killing power rendering the point essentially moot.
Marine Corps soldiers are already familiar with the "new" M4 as it has already been around for a while. However, only troop leaders were likely to have carried one as the everyday infantryman continued to pack the M16.
The M16 has a long and storied history going back to the Vietnam war when it was first used by US ground troops. Its use by the Marines is less though than the other branches of Service as many Marines continued to heft M14's, the "grandson" of the famed M1 Garand used throughout World War II and the Korean conflict.
According to the many Vietnam era vets, the M16 they carried was a completely different weapon that the M16 used by US forces today. "The early M16's were prone to malfunction, lacked corrosion resistance, jammed frequently and just generally weren't well-liked by foot soldiers," according to Robert Nelson, a Vietnam veteran with two tours as an infantryman. More history of the M16 can be found in the book, "The Gun". Today the M16 has undergone upgrades and modifications and has proven to be reliable and much better received by current troops.