Details
Coldfire 8.5-Inch Pistol-Gas 1:8 .300 BLK AR-15 Free-Float M-LOK Handguard Pistol Full Build Kit with Magpul BTR Brace
The Coldfire Full Build Kit is built around an 8.5-inch .300 Blackout heavy barrel machined from 4150 chrome moly vanadium steel, with a pistol-length gas system and a Parkerized finish. It is paired with a black free-float M-LOK handguard and a Magpul BTR pistol brace in black, mounted on a mil-spec heavy-duty six-position buffer tube. The kit ships with a complete bolt carrier group rated for 5.56, .223, .300 Blackout, and .350 Legend, along with a mil-spec quality M4 charging handle. The short, heavy barrel keeps the front end compact and sturdy, and the 1:8 twist suits a wide range of bullet weights in .300 Blackout. Lower receiver is not included. Lower parts kit, pistol grip, buffer, recoil spring, castle nut, and end plate details were not supplied with this listing.
Key Features
- 8.5-inch heavy profile barrel, 4150 chrome moly vanadium steel, Parkerized finish, 1:8 twist, .300 Blackout, 5/8x24 muzzle threads
- Pistol-length gas system with a micro low-profile gas block sized for a .750-inch barrel
- 7075-T6 aluminum upper receiver, anodized finish
- Free-float M-LOK handguard, black
- GI birdcage flash hider on 5/8x24 threads
- Complete AR-15 bolt carrier group (5.56/.223/.300/.350), 9310 alloy steel carrier, Nitride finish
- Mil-spec quality AR-15 M4 charging handle included
- Mil-spec heavy-duty six-position buffer tube
- Magpul BTR pistol brace, black
- Lower receiver is not included.
Barrel and Gas System
The 8.5-inch barrel is machined from 4150 chrome moly vanadium steel in a heavy profile and chambered in .300 Blackout, with a 1:8 twist rate suited to a wide range of bullet weights in this cartridge. It is finished in Parkerized black, a matte, corrosion-resistant treatment that gives it a clean, uniform look. The barrel runs a pistol-length gas system through a micro low-profile gas block sized for a .750-inch barrel. At the muzzle, 5/8x24 threads carry the included GI birdcage flash hider.
Upper Receiver and Handguard
The upper receiver is machined from 7075-T6 aluminum with an anodized finish, giving it a hard, wear-resistant surface that holds up to regular handling. It is paired with a black free-float M-LOK handguard. As a free-float design, it leaves the barrel free of handguard contact, and the M-LOK slots give the builder room to mount lights, grips, handstops, and other accessories.
Bolt Carrier Group and Charging Handle
The included complete bolt carrier group is rated for 5.56, .223, .300 Blackout, and .350 Legend, with a carrier machined from 9310 alloy steel and finished in Nitride, a surface treatment that adds hardness and corrosion resistance and helps the carrier stand up to repeated cycling. It is paired with a mil-spec quality M4 charging handle, completing the upper so it is ready to be matched with a compatible lower receiver.
Buffer Tube and Brace
The kit includes a mil-spec heavy-duty six-position buffer tube. A Magpul BTR pistol brace in black is included and is built to mount to a mil-spec carbine buffer tube like the one supplied in this kit.
Compatibility
This kit is built for AR-15 lower receivers and .300 Blackout builds. Handguard length, lower parts kit, pistol grip, buffer, recoil spring, castle nut, and end plate inclusion, as well as feed ramp style and ejection port door and forward assist configuration, were not supplied with this listing and should be confirmed before purchase.
Follow all manufacturer instructions and safe handling practices.
Ensure compliance with all applicable federal, state, and local laws.
