Members of Congress are driving the efforts, saying the switch to a single 5.56mm cartridge for all conventional U.S. forces stands to save American taxpayers considerable expense. It is likely to prompt a showdown between the two rounds favored by each service, raising the possibility the Marine Corps could be forced to adopt ammunition it rejected in 2009 because its early development was plagued by problems.
Marine Corps officials say they do not oppose the idea, provided the Army has fixed its round's propensity to wreak havoc by causing excessive wear on a weapon's inner workings. The problem stemmed from the M855A1's high chamber pressure and exposed steel tip, which could chew up a weapon's feed-ramp, erode barrels and crack bolts, said Col. Michael Manning, the program manager for Infantry Weapons Systems at Marine Corps Systems Command in Quantico, Virginia. The Marine Corps believes SOST is superior "at this time," he added, "but we are always open to testing and are participating in ongoing testing of the M855A1. We will always adopt whatever is best for the service."