The Ruger Mil-Spec AR-15 Buffer Tube Kit with M4 Stock (Ruger part no. 91007) is a factory-correct buffer tube and stock assembly from Ruger, built to the same mil-spec buffer tube diameter used on the company’s own AR-15-pattern rifles. That mil-spec sizing means the tube and its included stock drop onto any compatible mil-spec lower receiver, not just Ruger’s own guns, making it a straightforward fix for a worn or damaged buttstock assembly or a simple way to standardize a build around mil-spec parts. The kit ships fully assembled, with the collapsible M4-pattern stock already mounted to the tube, so there’s no separate stock to source or fit. It’s a practical, direct-fit upgrade for home-defense carbines, range rifles, or any mil-spec AR-15 build that needs a dependable, adjustable buttstock.

Key Specifications

• Machined to mil-spec buffer tube diameter, matching the tube Ruger uses on its own AR-15-pattern rifles for guaranteed stock and grip compatibility.
• Includes an M4-pattern collapsible stock with the industry-standard six-position design for quick length-of-pull adjustment.
• Stock body has a built-in sling loop at the toe, letting shooters attach a single- or two-point sling without extra hardware.
• Sold as a complete, pre-assembled kit, with the stock already mounted to the tube rather than shipped as separate loose parts.
• Comes with the castle nut and receiver end plate needed to mount the tube to the lower receiver’s buffer tube threads.
• Sized to house a standard carbine-length action spring and buffer weight for reliable bolt-carrier-group cycling.
• Mil-spec fit gives it broad cross-compatibility with mil-spec AR-15-style lower receivers beyond Ruger-brand rifles.
• Installs as a direct-fit replacement for a worn, damaged, or missing buffer tube and stock, with no gunsmithing required.
• Packaged as a single-part-number kit, replacing the tube, stock, spring, buffer, and mounting hardware all at once instead of piecing them together separately.

Frequently Asked Questions

Is this buffer tube mil-spec or commercial spec? It’s mil-spec, the same diameter Ruger uses on its own AR-15-pattern rifles, so it accepts standard mil-spec stocks and grips.

Does the kit include the stock, or just the tube? Both. The M4-pattern collapsible stock ships already mounted to the buffer tube as one complete assembly.

Will this fit any AR-15, or only Ruger-brand rifles? It’s built to the mil-spec standard shared across the AR-15 platform, so it fits mil-spec lower receivers beyond just Ruger’s own rifles.

Buy the Ruger Mil-Spec AR-15 Buffer Tube Kit with M4 Stock

Order this mil-spec buffer tube and M4 stock assembly directly from our Lubbock, Texas gun shop for fast, insured shipping straight to your door. It’s a factory-correct way to replace a worn tube, finish out a build, or standardize an AR-15 around mil-spec components, and it fits right alongside the rest of our gun parts and accessories lineup.