AR-15 Heavy Carbine Buffer Assembly | Mil-Spec Receiver Extension Kit for Carbine-Length Systems | SKU 100028018

Dial in smoother recoil, consistent lock-back, and dependable cycling with the AR-15 Heavy Carbine Buffer Assembly (SKU 100028018). Built around a mil-spec carbine receiver extension and a heavy carbine buffer, this kit provides the core timing components your AR needs for reliable operation—especially on suppressed, over-gassed, or hard-use patrol/training setups. Whether you’re refreshing a duty carbine or finishing a new build, this assembly brings durability, compatibility, and tuning headroom in one proven package.

What’s Included (Typical Kit Contents)

• Mil-Spec Carbine Receiver Extension (Buffer Tube) — 7075-T6 profile for strength and correct stock fit

• Heavy Carbine Buffer (H-class) — increased mass vs. standard to moderate bolt speed and soften impulse

• Carbine Action Spring — matched length/tension for carbine-length systems

• End Plate — standard profile; ready for most stocks and sling setups

• Castle Nut — secures the extension; stake for duty-grade retention

Note: Some runs ship with minor component variations (e.g., H vs. H2 buffer). Always verify the spec on your particular unit.

Why Go Heavy?

• Smoother recoil impulse: Extra buffer mass helps reduce felt recoil and muzzle dip, improving sight recovery shot-to-shot.

• Cleaner ejection & timing: Corrects “over-speed” carriers common on gassy or short-barrel builds for more consistent ejection patterns and positive lock-back.

• Suppressed optimization: Heavier buffers mitigate the additional backpressure of suppressed systems, supporting reliability and parts longevity.

• Wear reduction: Lower bolt velocity = less battering of lugs, pins, and receiver extension internals.

Compatibility

• Platform: AR-15 / M4 pattern lowers

• Receiver Extension: Carbine-length only (6-position stocks, mil-spec diameter)

• Gas Systems: Carbine, mid-length, and many 14.5–16" uppers; tune alongside gas port and ammo

• Stocks: Fits mil-spec-diameter adjustable stocks (not commercial-diameter)

• Not for: A5/Intermediate extensions, rifle-length extensions, or AR-10/.308 pattern rifles

Installation (Best Practices)

1. Verify clear & safe. Separate upper/lower.

2. Thread receiver extension into the lower; capture the buffer retainer and spring.

3. Align end plate over the rear takedown detent/spring; snug the castle nut against the end plate.

4. Torque & stake the castle nut (duty builds): 38–40 ft-lb typical; stake in two places.

5. Insert carbine spring + heavy buffer (bumper toward the rear).

6. Function check: Confirm smooth cycling and lock-back on an empty magazine.

Pro Tip: Pair this kit with an adjustable gas block or correct gas port sizing for a truly balanced system—especially on SBRs and suppressed rifles.

Troubleshooting & Tuning

• No lock-back: Check gas block alignment, ammo, and spring condition. Ensure carbine-length parts in a carbine tube (don’t mix rifle/carbine components).

• Brass at 1–2 o’clock (over-gassed): Heavier buffer (H2/H3) or gas adjustment may help.

• Short-stroking: Try standard/heavy buffer swap, verify gas leak points, and confirm bolt carrier/buffer movement without binding.

Who It’s For

• Suppressed carbines needing slower bolt speed and flatter recoil

• Duty/home-defense builds where reliability and longevity are non-negotiable

• Training/range rifles chasing consistent ejection and softer impulse

• New builders wanting a complete, matched mil-spec buffer solution

Care & Maintenance

• Keep the receiver extension lightly lubed—avoid heavy grease that traps grit.

• Inspect buffer bumper and roll pin; replace at signs of peening or cracking.

• Replace action springs periodically (3–5k rounds typical; sooner for high-heat/suppressed use).

Key Features at a Glance

• Mil-Spec Carbine Receiver Extension (7075-T6)

• Heavy Carbine Buffer (H-class mass for improved timing)

• Matched Carbine Action Spring

• End Plate & Castle Nut included

• Designed for Carbine-Length Systems (not rifle/A5)

• SKU: 100028018

Specifications

SEO Highlights (for Merchandising & Search)

AR-15 heavy carbine buffer assembly, mil-spec carbine receiver extension kit, H buffer AR-15, carbine buffer tube with spring and castle nut, suppressed AR recoil reduction, reliable last-round lock-back, 6-position stock buffer kit, SKU 100028018.

Balance your gas, tame your recoil, and boost reliability—drop in the AR-15 Heavy Carbine Buffer Assembly (SKU 100028018) for a smoother-running, duty-ready carbine.
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