The US Special Operations Command (SOCOM) is seeking something a little smaller than its existing M4A1 and Mk.18 carbines: The command just released a request for information (RFI) to the industry seeking proposals for conversion kits for M4A1 Carbine receivers that turn the weapons into sub-6lb, sub-26″ .300 Blackout caliber weapons. The RFI was released on March 9th, and submitting companies have until 3 PM Eastern on April 10th to respond. The RFI’s requirements read:

PDW Kit specifics: The kit must be adaptable to the standard M4A1 lower receiver, any modification to the lower receiver must be reversible and nonpermanent. The kit must be in .300 Blackout (BLK) cartridge, total system weight, including the M4A1 lower in not to exceed 5.5lbs. Length with stock extended not to extend 26″ length with stock collapsed or folded shall be 17″ (T), 15″ (O) and a height not to exceed 7.5″. Weapon shall be fully functional when collapsed or folded. Kit should include a 5.56mm barrel that can be changed from .300 BLK to 5.56mm in less than 3 minutes. Accuracy shall be 3.0 MOA (T), 2.0 MOA (O) @100 yds. and 5.0 MOA (T), 3.0 MOA (O) @ 300 yds. both in .300 BLK supersonic.

To meet these requirements, it is necessary to either dramatically shorten or do away with the AR-15’s receiver extension and buffer, even when using very short barrels. Colt’s 10.3″ barreled Sub Compact Weapon (SCW) for example, is 28.5″/30.25″ (collapsed/extended) with the stock unfolded, and 23.5″ with the stock folded, meaning that this weapon could not meet SOCOM’s requirements except with a 3.8″ barrel! Even SIG’s MCX, which uses no buffer tube and has a fully folding stock, would need a barrel just 6.5″ long to meet this requirement, and it would still struggle to meet the 5.5lbs weight limit.

In other words, these are extremely tough requirements to meet for an M4 conversion kit, especially since submissions must be made before April 10th! Best of luck to any companies who decide to make a submission!

H/T, soldiersystems.net