SOCOM has launched the Hypervelocity Improved Carbine (HICAR) program to develop an M4 upper receiver capable of firing a higher-pressure M855A1+ round. The goal is to extend effective engagement ranges from roughly 300 meters to 600 meters and beyond while keeping the carbine lightweight. M855A1+ is specified at about 82,000 psi, which increases velocity but raises durability concerns for weapons not designed for that pressure. White papers are due June 8; industry pitch meetings are scheduled for September 15 and 16.
SOCOM Seeks 'Hypervelocity' M4 Upper To Fire M855A1+ And Extend Effective Range To 600m+
Pfc. Andrew Shaw participates in an M-4 qualification at Studnica Range, Drawsko Pomorskie Training Area, Poland, Sept. 15, 2021. (Spc. Max Elliott/Army)(Spc. Max Elliott)
U.S. Special Operations Command (SOCOM) has launched the Hypervelocity Improved Carbine (HICAR) effort to extend the service life of the legacy M4 carbine by developing a new upper receiver capable of firing a higher-pressure hypervelocity variant of the 5.56x45mm NATO round, designated M855A1+.
Solicitation Highlights
The recent SOCOM solicitation requests proposals for an M4 upper designed to handle emerging hypervelocity ammunition modeled on the 5.56x45mm cartridge. SOCOM says HICAR will "leverage the performance benefits of current and future experimental hypervelocity rounds" to help close anticipated battlefield capability gaps.
Fired from a standard-issue M4, the current M855A1 cartridge has a recognized effective range of about 300 meters. The HICAR upper aims to let operators engage targets at significantly greater distances — SOCOM specifies a desired effective range of 600 meters and beyond — while preserving the portability and ergonomics of a lightweight carbine.
Ammunition Pressure And Durability Concerns
The solicitation states that M855A1+ is loaded to roughly 82,000 pounds per square inch (psi) of chamber pressure. Higher chamber pressure typically increases muzzle velocity and effective range, but it also raises stresses on barrels, bolts and other components. Firearms not engineered to withstand those pressures can experience accelerated wear or catastrophic failure.
Testing, Timeline And Related Programs
White paper submissions for HICAR are due June 8. SOCOM plans industry pitch meetings on September 15 and 16. During qualification testing, participating M4 uppers are expected to fire 600 rounds, composed primarily of M855A1+ with some M855A1 for comparison.
The HICAR effort runs alongside other SOCOM modernization activities: SOCOM announced it will begin fielding the MK24 Medium Range Gas Gun rifle family (chambered in 6.5mm Creedmoor and .338 Norma Magnum) before the end of the fiscal year. Meanwhile, the U.S. Army and U.S. Marine Corps have been transitioning away from the original M4 platform toward the Next Generation Squad Weapons and the M27 Infantry Automatic Rifle, respectively.
Bottom line: HICAR aims to extend the M4's engagement envelope by combining advanced materials and weapon design with higher-performance ammunition — but doing so requires careful engineering to manage increased chamber pressures and preserve reliability.
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