Weapons submitted included the XCR by Robinson Armament Co., an off-the-shelf or derivative of the M6A4 by LWRC, the ACR by Remington, the SR-16 by Knight's Armament Company, the FN SCAR by FN Herstal, the CM901 by Colt's Manufacturing Company, and the HK416 by Heckler & Koch. A draft request for proposal (RfP) was issued in late 2010 followed by an industry day. The finalized RfP was issued in second quarter FY 2011 to which industry had a month to respond. A 12–18 month testing phase will commence and over 1 million rounds will be fired. Testers will look at the consistency in accuracy of the carbines as they age. Costs will also be considered. The Office of the Secretary of Defense will monitor tests and the evaluation and there will be congressional oversight to ensure the competition is full and open. US$30 million will be spent on testing. The winner of the competition must be a "measurable improvement" over the M4 carbine to replace it; otherwise, the program will instead convert all M4 carbines to the enhanced version. The winner of the competition will sell their rights to their weapon to the military and choose two other competing suppliers to help manufacture it.
As for fielding a possible winner, the Army has over 1.1 million armed personnel, approximately half are front-line combat brigades. If a new carbine is selected, the Army would see 500,000 purchased for infantry brigade combat teams (IBCT), and the existing and improved M4s given to support troops to replace their M16s. If the improved M4 turns out to be the winner and the new carbine program is scrapped, then the IBCTs will likely be fitted with the improved M4s, and the existing M4s would again be given to support troops to replace their M16s. On November 17, 2011 the US Marine Corps announced they will not participate or adopt any new weapon which may or may not come out of the competition. The USMC said they will continue to use standard M4s and M16A4s. They did mention they are considering upgrading the M16A4