Colt’s Purchase of LWRC: Will US Troops Get a New Rifle?

[LRRPF52]

Every time a new cartridge is introduced, it changes the original well thought out plan of the AR 15 rifle. Gene designed a fabulous 20" rifle that functioned perfectly with the m193 cartridge it was designed for. When the m855 was introduced, much thought and research was put into assuring the the chamber and gas port pressures remained the same as not to affect reliability. Then they decided to chop 6" off the barrel, and and 5.5" off the gas length for the M4. This changed everything. Bolts and extractors are now subjected to considerably more stress. The gas port and chamber pressures doubled, and the gas port had to be shrunk. To add a new cartridge to the mix would simply add to the reliability issues the M4 already faces during heavy sustained fire, not to mention logistics. It wouldn't surprise me if they did change calibers in their infinite wisdom, but it would only heap more problems on an already problematic weapons system. Just my .02.

The AR15 was not designed for the M193 5.56x45 (pre-NATO adoption designation of the 55gr FMJBT with cannelure high pressure .223 Remington). Gene Stoner and his team scaled up a rifle using the AR10's design, around the .222 Remington after Armalite was solicited to provide a Small Caliber High Velocity Rifle for the minority contingent of the CONARC/Infantry Board in 1957.

Spring: The Infantry Board extends the original 300 yard "ideal" to 400 yards in order to pacify certain CONARC members, and once again to 500 yards, to insure acceptance at the Pentagon. The finalized request calls for a 6 pound, select-fire .22 caliber rifle with a conventional stock and a 20 round magazine. The proposed chambering has to penetrate the issue steel helmet, body armor, and a .135" steel plate at 500 yards, while maintaining the trajectory and accuracy of M2 ball from a M1 rifle, and equaling or exceeding the "wounding" ability of the .30 Carbine.

http://www.thegunzone.com/556dw-1.html

Remembering General Wyman's favorable bent toward the AR-10 design, ArmaLite had also begun work on a scaled down version of the rifle. But this design, credited to John Peck, also uses the same small barrel extension as the AR-11. After the failure of the AR-11's barrel extension in testing, work is discontinued on Peck's design. Robert Fremont and L. James Sullivan are eventually tasked with starting from scratch in scaling down the AR-10 to .222 Remington.

The short barrel AR15's originated as part of Colt's attempt to introduce a family of weapons based on the AR15 in 1963, including:

* The Colt 605 Infantry Leader's Carbine (15" barrel, RLGS)
* The Colt 606 Heavy Barrel Squad Automatic Rifle
* The Colt 607 Commando
* The Colt 608 USAF Survival Carbine
* A belt-fed LMG AR15

This family of weapons was introduced as "CAR-15", and that name was eventually associated with some later Commando variants that weren't even part of the CAR-15 family you see here.


There was no chopping off 6" for the M4. The M4 is a descendant of the following lineage:

* Colt 607
* XM177E1
* XM177E2
* Colt Model 653 (the first 14.5" production carbine in the early 1970's for SEAL's and Ranger Regiment, as well as other SOF units)


* Colt Model 723
* Colt Model 727
* XM4
* M4A1

No chamber pressures are doubled, as that would be 124,000psi (5.56 MAPx2). An M4 chamber pressure is the same as an M16A2 chamber pressure. Locating the port closer to the chamber will result in a higher port pressure, which is mitigated with port sizing and buffer weight.

I had no issues with the M4 and M4A1 carbine while on active duty, and have conducted Close Quarters Marksmanship range sessions where 1,100 rounds of 5.56 M855 were run through my carbine in about 4 hours, all rounds in COM of B27 targets.

Of all the assault rifles I have used around the world, literally from Asia to South America to Europe to the Middle East, the M4 shines at the top of the list in terms of reliability. I can't think of many assault rifles that can undergo high volume shoot training like an M4 can.