LBE Unlimited H3 Heavy Recoil Buffer Tube Kit 6-Position Mil-Spec - Black - H3BUFKT - UPC: 706612408110
Product Description
The LBE Unlimited H3BUFKT is a heavy-duty 6-position mil-spec receiver extension assembly equipped with an H3 heavy recoil buffer for AR-15 carbines, short-barreled rifles (SBRs), pistol-caliber carbines (PCCs), and suppressed weapon systems. Designed as a comprehensive rear lower receiver staging solution, this kit equips armorers and custom builders with a 6-position mil-spec receiver extension tube, carbine action spring, H3 heavy buffer, steel castle nut, and receiver end plate.
At the core of the system is an H3 heavy recoil buffer weighing approximately 5.4 ounces, configured with three internal tungsten weights. This substantial reciprocating mass delays bolt carrier unlocking, tames aggressive cyclic rates, and increases dwell time. The added inertia is engineered to resolve gas-overpressure issues commonly encountered in short-barreled carbines (such as 10.3" to 11.5" configurations), heavy suppressor backpressure setups, and full-auto or rapid-fire operations where smooth extraction and bolt-bounce elimination are critical.
The 6-position receiver extension tube is precision-machined from high-grade 7075-T6 aluminum and finished in a matte black hardcoat anodize for maximum wear, chemical, and corrosion protection. Standard mil-spec outer dimensions ensure seamless compatibility with aftermarket collapsible stocks. The kit includes a high-tensile carbine recoil spring, steel receiver end plate, and heavy-duty castle nut designed for proper torquing and double-staking.
*Armorer Bench Notes & Real-World Staging Guidance:
Gas System & Buffer Tuning Matrix:
• Primary Application: Heavily over-gassed short-barrel carbines (10.3"–11.5"), suppressed 5.56 NATO / .300 Blackout carbines, and high-recoil PCC setups.
• Stock Fitment: Mil-spec diameter 6-position tube (accepts standard mil-spec collapsible stocks).
Lower Receiver Assembly Steps:
1. Lightly coat the external threads of the aluminum buffer tube and inner bore walls with high-grade gun oil before assembly.
2. Thread the castle nut and receiver end plate onto the receiver extension, then thread the extension into the lower receiver until it captures the rear takedown pin detent and spring.
3. Depress the buffer retainer pin and spring into its lower pocket and seat the front lip of the buffer tube flush over the edge of the retainer pin.
4. Torque the castle nut to 38–40 ft-lbs using an armorers castle nut wrench, and stake the steel end plate twice into the castle nut notches using an automatic center punch.
Key Features
- Complete drop-in rear lower receiver extension assembly for AR-15 and SBR platforms.
- Includes H3 heavy recoil buffer (~5.4 oz) with three tungsten weights to delay bolt unlocking.
- 6-position mil-spec receiver extension tube constructed from 7075-T6 aluminum.
- Matte black hardcoat anodized finish provides scratch resistance and low-glare presentation.
- High-tensile carbine recoil spring delivers uniform forward bolt feeding energy.
- Includes steel receiver end plate and heavy-duty castle nut for secure installation and staking.
- Proudly manufactured in the USA by LBE Unlimited.
Product Specifications
- Brand: LBE Unlimited
- MPN / Model: H3BUFKT
- UPC: 706612408110
- Tube Type: 6-Position Mil-Spec Diameter
- Tube Material: 7075-T6 Hard-Anodized Aluminum
- Buffer Weight: H3 Heavy (~5.4 oz)
- Spring Type: Carbine Length Recoil Spring
- Hardware Included: Buffer Tube, H3 Buffer, Recoil Spring, End Plate, Castle Nut
- Platform Fitment: AR-15 / M4 / SBR Lower Receivers
