DPMS Quad-Rail Features The DPMS Quad-Rail is built around a 16 chrome-moly vanadium steel barrel finished in nitride for corrosion resistance carrying a 1:7 twist rate that stabilizes both lightweight and heavier 5.56 NATO bullet weights. The barrel is threaded 1/2x28 and finished with an A2-style flash hider while an M4 barrel extension and carbine-length gas system contribute to reliable cycling across a range of ammunition. The bolt carrier group uses a full-auto profile carrier machined from 8620 steel paired with a shot-peened mil-spec Carpenter 158 steel bolt hardened to USGI specifications and properly staked for long-term durability. A low-profile gas block keeps the barrel profile clean while maintaining consistent gas pressure for the action. The forged 7075-T6 upper receiver is machined to mil-spec tolerances and hard-coat anodized including a forward assist and dust cover for a complete mil-spec-configured upper. The matching forged lower receiver uses the same 7075-T6 aluminum and hard-coat anodized finish fitted with a mil-spec diameter buffer tube offering 6 positions of stock adjustment. A DPMS Retro A2 pistol grip and Retro aluminum trigger guard round out the lower s furniture while a 13.5-inch DPMS M-Lok free-float handguard replaces the classic quad-rail with a lighter more versatile accessory mounting system. Built entirely from mil-spec components in the USA the DPMS Quad-Rail delivers dependable performance for range use home defense or duty-style training. DPMS Quad-Rail Specifications Brand: DPMS Model: DPM4 Quad-Rail Type: Modern Sporting Rifle Caliber: 5.56 Capacity: 30 Rounds Barrel Length: 16 Barrel Description: Threaded M4 Profile Barrel Material: Chrome Moly Vanadium Twist Rate: 1:7 Muzzle Thread Pattern: 1/2x28 Muzzle Device: A2-Style Gas System: Carbine Length Receiver Material: Forged 7075-T6 Handguard: 13.5 DPMS M-Lok Grip: DPMS Retro A2 Pistol Grip Color: Black Finish: Anodized Stock: M4 Collapsible Compatible Hosts: Picatinny Rail Overall Length: 32 Weight: 6.8 lbs Available At: GrabAGun