After months of heated debate, the Army will conduct a side-by-side test shoot next month with its standard-issued carbine to see how well it can withstand extreme dust and sand environments.
The tests, which will be conducted at the Army's Aberdeen Test Center in Maryland, will include three other rifles some say are better constructed to withstand the grueling environmental conditions often found in Iraq and Afghanistan.
The service yielded to critics - particularly lawmakers in Congress - who recently ratcheted up the debate over whether the current M4 carbine, manufactured by Colt Defense, is more susceptible to jamming in dusty conditions than other weapons used by Soldiers and special operators.
"The Army agreed to conduct testing of four carbine designs in an extreme dust environment," said Lt. Col. Timothy Chyma, product manager for individual weapons with Program Executive Office Soldier, in an email to Military.com.
"The test results will inform the U.S. Army Infantry Center in the development of a potential new carbine requirement as part of their ongoing capabilities based assessment."
In April, Sen. Tom Coburn (R-Okla.) insisted in a letter to then-acting Army Secretary Pete Geren that better weapons technology is available that can guard against stoppages stemming from dust and sand interfering with the firing mechanism of the M4.
The Army's carbine uses a gas system that evidence shows is susceptible to stoppages unless it is frequently cleaned.
The shoot off will test the capabilities of the M4/M16 operating system against three other rifles: the Heckler and Koch-built HK416, the FNH USA-designed Mk16 SOCOM Combat Assault Rifle and the previously-shelved, H&K-manufactured XM8 carbine.
All three competitors use a gas-piston operating system that requires less maintenance and has demonstrated in some tests that it can fire accurately even if completely fouled with sand, dust and mud.
"Considering the long standing reliability and lethality problems with the M16 design, of which the M4 is based, I am afraid that our troops in combat might not have the best weapon," Coburn wrote in April. "A number of manufacturers have researched, tested and fielded weapons which, by all accounts, appear to provide significantly improved reliability."
A December 2005 Center for Naval Analyses study commissioned by the Army indicated the M4 - when properly cleaned - exhibited few stoppages. But 20 percent of those who had complications with their M4s said they experienced bad enough jams that they had to pull out of the fight.
Many special operations units favor the HK416, due in part to its increased reliability. This month, Special Operations Command began operational tests on the Mk16 and the heavier-caliber Mk17 to eventually replace its M4 and HK416 stocks.
The sand tests will include 10 samples of each weapon through which engineers will fire 6,000 rounds. Each weapon and loaded magazine will be exposed to "extreme dust" for 30 minutes then test fired with 120 rounds, Chyma said.
"Each weapon will be wiped down and lubricated every 600 rounds with a full cleaning every 1,200 rounds," Chyma added. "The firing, collection of data and analysis of data is expected to take approximately five months."
Coburn said in his April letter to Geren that even though the M4 works, better weapons exist. He was so insistent that the Army compete new M4 contracts to outfit its expanded brigade combat teams that he placed a hold on the Geren nomination to become Army secretary until the service relented, a Coburn staffer confirmed.
The Army's willingness to hold the limited "sandstorm shoot-off" released the nomination, and Geren was confirmed by the Senate July 13.
The side-by-side sand tests "will be part of the ongoing Army assessment and requirements process - with the ultimate goal of continuing to provide the best possible weapons and equipment to our Soldiers," said Army spokesman, Lt. Col. William Wiggins.