Historical Background 

The lineage of Windham Weaponry is deeply rooted in American firearm manufacturing heritage, bringing together a veteran team of gunsmiths and craftsmen dedicated to producing duty-grade firearms. Combining precise engineering with specialized platform designs, Windham Weaponry engineered dedicated pistol-caliber systems built to deliver lightweight handling, low recoil, and tactical versatility across home-defense and pistol-caliber carbine (PCC) roles.

Within Windham Weaponry’s catalog, the 9mm GMC (Glock Magazine Compatible) Series—offered in both 9mm Carbine (R16FTT-9MM) and 9mm Pistol (RP9SFS9MM) configurations—was developed to bridge the gap between traditional AR ergonomics and ubiquitous pistol magazine compatibility. Engineered specifically to accept standard double-stack Glock-style 9mm magazines, the GMC line offers affordable training, shared ammunition/magazine logistics with duty sidearms, and rapid target engagement.

Technical Overview

Unlike traditional gas-operated ARs, both Windham Weaponry 9mm GMC models utilize a blowback operating system tuned specifically for 9x19mm Parabellum/Luger cartridges. The series features a custom lower receiver with a dedicated Glock magazine well, integrated magazine catch, ejector, and an internal last-round bolt hold-open mechanism. The GMC Carbine uses a 16-inch barrel for maximum 9mm velocity and stabilization, while the GMC Pistol utilizes a compact 9-inch barrel paired with a stabilizing arm brace for supreme maneuverability in tight quarters.

Construction & Receivers

• Upper & Lower Receivers: Machined from high-strength milled billet or forged 7075 T6 aircraft aluminum, finished in a durable black hardcoat anodize. The lower features a dedicated angled Glock magazine well with an integrated trigger guard and an oversized magazine release lever. The upper is a slick-side flat-top configuration (eliminating the forward assist and ejection port cover unnecessary for 9mm blowback action) with a integrated last-round bolt hold-open mechanism.

• Barrels & Metallurgy: The barrels are crafted from heavy-duty 4150 Chrome Moly Vanadium (11595E) steel treated with a corrosion-resistant Melonite QPQ finish inside and out. Cut with a 1:10 (RH) twist rate, the barrels accurately stabilize a broad spectrum of 9mm projectile weights (from 115-grain target ammo to 147-grain heavy defensive subsonic loads).

  • GMC Carbine Barrel: 16-inch medium profile, threaded 1/2×28 TPI with a thread protector.

  • GMC Pistol Barrel: 9-inch medium-light profile, threaded 1/2×28 TPI with a knurled thread protector.

• Bolt Assembly: Features a dedicated blowback bolt assembly machined from heavy 8620 steel with a black phosphate finish, weighted properly to delay unlock timing and ensure reliable extraction without excessive bolt bounce.

Furniture & Ergonomics

• Handguards:

  • GMC Carbine: Fitted with a 13-inch free-floating aluminum M-LOK handguard featuring a continuous top Picatinny rail for optics and accessory attachment.

  • GMC Pistol: Fitted with a 7-inch free-floating aluminum M-LOK handguard with a top Picatinny rail.

• Controls & Furniture:

  • GMC Carbine: Equipped with an A2 black polymer pistol grip and a standard 6-position telescoping M4-style buttstock.

  • GMC Pistol: Equipped with an A2 pistol grip and a 5-position SB Tactical SBA3 pistol stabilizing arm brace mounted on a mil-spec buffer tube.

• Muzzle Device & Magazines: Both variants feature un-suppressed target thread protectors on standard 1/2×28 threads, making suppressors or compensators easily adaptable. Ships factory-equipped with one 17-round Magpul PMAG 17 GL9 magazine and accepts all standard OEM Glock 17/19 9mm double-stack magazines as well as high-capacity factory drums and extended sticks.