M4A1 SOCOM Block 1 Colt Upper Receiver Group 14.5" pinned and welded

The Colt M4A1 SOCOM Block I upper receiver group — a 14.5" Colt SOCOM-profile barrel with A2 flash hider pinned and welded to 16.1" overall, fitted with the mil-spec M4 RAS rail, Matech BUIS, and a Colt complete BCG. Clone-correct to the Block I configuration fielded at the start of the Global War on Terror.

• Clone-correct M4A1 Block I: the Colt-built configuration that launched the SOPMOD Block I program in the late 1990s / early 2000s.
• Colt SOCOM-profile 14.5" barrel — heavier profile than the standard M4 contour, with M203 cuts.
• Pinned and welded A2 flash hider for a non-NFA 16.1" OAL — street-legal without a tax stamp.
• Mil-spec M4 RAS quad rail with three rail covers — the Block I handguard.
• Colt complete BCG and Matech Picatinny-logo rear BUIS.

SOPMOD Block I was the U.S. Special Operations Command's first formalized accessory package for the M4A1 carbine, initiated in the late 1990s and widely fielded by the early 2000s. The defining Block I hardware is the Knight's Armament M4 RAS quad rail, the Trijicon ACOG or Aimpoint M68 / Comp M2 optic, the AN/PEQ-2 IR laser, and a Surefire M951 or M952 weapon light — all mounted on a Colt 14.5" SOCOM-profile barrel. The SOCOM-profile barrel is heavier than the standard M4 contour and is the barrel specified for sustained semi-automatic and suppressed fire; the profile also carries the M203 grenade launcher cuts from the factory.

This upper is a genuine Colt build — Colt upper receiver with interior white T-marks, Colt SOCOM-profile barrel, Colt F-height FSB timed and installed at the Colt plant, and a Colt complete bolt carrier group. The barrel is pinned and welded at the A2 flash hider to an overall length of 16.1", which makes the upper street-legal as a non-NFA rifle barrel. Colt is not currently marking every F-height FSB with the "F" stamp, but the FSB on this upper is an F-height unit, correctly timed by Colt.

The 14.5" Colt SOCOM barrel is chrome-lined, 1:7 twist, MP-tested, chambered in 5.56 NATO, and will stabilize the full range of issued loads — M193 55-grain, M855/SS109 62-grain, and the Mk262 Mod 1 77-grain OTM round favored for SOCOM precision work. The complete Colt BCG carries a C-158 bolt, MPI and HP tested, with a tool-steel carrier and staked gas key. This is the same bolt carrier group Colt ships on contract rifles.

Specifications:

• Upper receiver: Colt forged M4, interior white T-marks, CAGE-code marked
• Barrel: Colt 14.5" SOCOM profile, 1:7 twist, chrome-lined, 5.56 NATO
• Overall barrel length: 16.1" after pin-and-weld (non-NFA)
• Muzzle device: A2 flash hider, professionally pinned and welded
• Gas system: Carbine length, F-height FSB factory-timed by Colt
• Handguard: Mil-spec M4 RAS quad rail with three rail covers
• Rear sight: Matech Picatinny-logo BUIS
• BCG: Colt complete, C-158 bolt, MPI/HP tested, staked key
• Finish: Factory Colt finish; minor surface marks consistent with new Colt production

The Block I is where most clone builders start, and for good reason — it is the carbine that fought the first decade of GWOT, the parts are still recognizable, and a Colt-built Block I with the right RAS and the right barrel pin-and-weld is as solid a foundation as the platform gets. We keep these built up when we can. Copy that — grab one while they're here, and we'll get it out fast.