Ridgeline Defense RDM4 Upper Receiver Group (R)

Upper Includes: Ridgeline Defense Bolt Carrier Group / Standard AR15 Charging Handle / A2 Flash Hider (NOT Pin & Welded)

The culmination of over a century of combat and competition experience; merged with cutting edge design, engineering, and an uncompromising devotion to quality and performance. Unlike other companies, we are the end users. There is nothing lost between our requirements and the final product, just a group of dedicated professionals who have all carried guns into harm’s way committed to bringing you the world’s finest fighting rifles. Our rifles, like our training, are built on the belief that there is nothing advanced, just the perfect execution of the basics. Every component is individually inspected before assembly, then the rifles undergo a multi-step inspection and test fire process with a two-person verification to ensure that nothing goes out the door we wouldn’t bet our lives on.

FORGED RECEIVER SET – RDM4 receivers our machined to exacting tolerances from 7075 T6 Aluminum forgings. We specifically call out dimensions that ensure a thermal fit for barrel installation and press fit of the upper and lower receiver. They are finished in Type-3 Hardcoat Anodize.

COLD HAMMER FORGED CHROME LINED BARREL, 11.5 INCH or 14.5 INCH – Ridgeline barrels feature hammer forged using the same proprietary high-grade Chrome Moly Vanadium steel used in machine gun barrels, designed to handle the punishment of sustained fully automatic fire. After forging, each barrel is Magnetic Particle tested to ensure that it is free of micro stresses or flaws, resulting in consistency and quality in every barrel. The bore and chamber are chrome lined to help resist corrosion and provide resistance to heat erosion which greatly improves barrel life and reliable chambering/extraction. The M4-style feed ramps and barrel extension provide consistent feeding and the matte black Manganese Phosphate finish resists external corrosion and oxidation. Prior to assembly, each barrel is inspected and gauged for straightness, concentricity, gas port size, and head space to ensure accuracy and reliability. Chambered in 5.56 NATO, our barrels feature a 1:7 twist rate designed to stabilize a wide range of bullet weights from 55-90gr.

GAS SYSTEM – Our gas block features an indexing tab and dual-taper attachment method utilizing a jam-nut that threads on to the barrel itself, negating the use of set screws or pins drilled counter to the gas port. This method allows us to hold very tight tolerances as the system becomes completely sealed, unlike a standard gas block that must be “pulled” down and into contact with the gas journal. This ensures that when the system becomes pressurized during firing, and even more so with suppressor use, we have a consistent amount of gas shot after shot. Furthermore, we utilize heat-treated 4140 CM steel with our CMV barrels to best match the thermal properties of the competing parts.

RIDGELINE FULL-AUTO RATED BOLT AND CARRIER – The Ridgeline Defense Bolt Carrier Group is Full-Auto rated and machined to USGI specifications utilizing a Mil Spec Carpenter 158 steel bolt that has been Magnetic Particle Inspected (MPI) and High Pressure Tested (HPT). Carrier keys are chrome lined, heat treated, gauged prior to assembly, and properly staked in accordance with USGI specifications. Finished with Manganese Phosphate and chrome lined per USGI spec.

RIDGELINE MLOK HANDGUARD – Our handguard was built to be more rigid than the industry standard making it a perfect host for mission- essential enablers such as lights or aiming lasers. Machined from a 6061 T6 Aluminum extrusion, our rail features m1913 picatinny on the top and MLOK attachment on seven sides, T-slot engraving, anti-rotational tabs and mounting hardware, and is finished in Type 3 hardcoat anodize. It mounts to the upper receiver via a 2.75” steel barrel nut using our CAMLOCK attachment system, providing uniform direct pressure to rail/receiver interface.

Proudly made in the USA.

NFA DISCLAIMER/WARNING: The 11.5″ and 14.5″ (not Pin and Welded) do not meet the 16″ minimum barrel length requirement, and requires registration and a tax stamp with the Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE) when assembled into a complete rifle. Additional state and local restrictions may apply. It is the sole responsibility of the buyer to comply with any and all applicable laws.