AR-15 Buffer Weight Chart: H, H2 and H3 Explained

An AR-15 buffer weight chart answers one question: how much mass sits behind your bolt carrier. A standard carbine buffer weighs about 3.0 oz, an H buffer about 3.8 oz, an H2 about 4.6–4.7 oz, and an H3 about 5.4–5.6 oz. Heavier buffers slow the carrier down, which helps short barrels, suppressed rifles and reset devices like the Super Safety run reliably. If you’re choosing firearm parts and accessories for a new build or tuning one that already runs, start with the chart below. The right buffer is the lightest one that makes your rifle run reliably with the ammo you actually shoot.

What Does a Buffer Weight Do?

The buffer sits behind the bolt carrier inside the receiver extension, the tube that runs into the stock. When the rifle fires, gas drives the carrier back. The buffer and spring absorb that energy, stop the carrier, and push it forward again to strip the next round from the magazine.

A heavier buffer slows the carrier’s rearward travel and delays unlocking. That extra time lets chamber pressure drop before the bolt opens, which means smoother cycling, less wear on the bolt and extractor, and a softer recoil impulse. A heavier buffer also carries more momentum on the way forward, which helps the bolt lock reliably when the rifle is dirty. Too much weight, though, and the carrier may not travel far enough to pick up the next round or lock back on an empty magazine.

Why Do H3 Buffer Weights Vary by Brand?

“H3” describes a configuration, not an exact weight. Most H3 buffers use three tungsten weights, but the body material and the size of each weight differ between makers. Published H3 weights include BCM at 5.4 oz, Spikes Tactical at 5.4 oz, KAK at 5.5 oz, Aero Precision at 5.6 oz, and some 7075-aluminum-body H3s at 5.2 oz. The same is true one step down: some buffers sold as “H2” weigh 4.0–4.3 oz instead of the usual 4.6–4.7 oz.

For most rifles, a 0.2 oz difference won’t matter. For a rifle that’s right on the edge of its timing, such as a short-barreled, suppressed or reset-trigger build, it can. If your rifle is sensitive to timing, compare the ounce rating, not just the label.

Which Buffer Weight Should You Use for Your Gas System?

Gas system length and barrel length set how hard and how early the carrier moves. Shorter gas systems tap gas closer to the chamber, where pressure is higher, so they usually need more buffer weight. These are common starting points; sources disagree at the edges, so test before you settle on one:

• Pistol-length gas (7.5–10.5 in barrels): start at H2; move to H3 for 9–11.5 in barrels.
• Carbine-length gas (10.3–16 in): H1 or H2 for 14.5–16 in barrels; H2–H3 for 10.3–12.5 in.
• Mid-length gas: carbine buffer or H1.
• Rifle-length gas: rifle buffer with a fixed rifle stock, or a carbine or H1 buffer in a carbine tube.

A rifle buffer and an H3 weigh about the same, but they’re not interchangeable. The rifle buffer is longer and needs a rifle-length receiver extension and spring. Putting a carbine buffer in a rifle tube, or the reverse, leaves the carrier with the wrong amount of travel.

Does the Buffer Spring Matter Too?

Yes. The buffer and spring work as a pair. A standard carbine spring is matched to carbine through H3 buffers, while an extra-power or flat-wire spring adds return force without adding mass. Some shooters solve light overgassing with a stronger spring instead of a heavier buffer, and some use both. If you change one, test the rifle again before changing the other. Replace the spring when it’s worn or shorter than spec, because a tired spring can make even the right buffer weight feel wrong.

Do You Need a Heavier Buffer When Suppressed?

Usually one step heavier. A suppressor increases backpressure, which makes the carrier move faster and harder and sends more gas back toward the shooter’s face. Many shooters go from a carbine or H buffer to an H2, and from H2 to H3 on short carbine-gas rifles.

A heavier buffer doesn’t reduce the gas itself, though. If your rifle is badly overgassed when suppressed, an adjustable gas block fixes the cause; a heavier buffer only manages the symptom. Many suppressed rifles end up with both: an adjustable gas block set for the can, and an H2 or H3 to smooth out what’s left.

What Buffer Weight Do You Need for a Super Safety or FRT?

Reset devices depend on timing. A super safety or forced-reset trigger needs the bolt carrier to stay back long enough for the reset to finish before the carrier returns to battery. A light buffer in an overgassed carbine can outrun that window, which shows up as dead trigger pulls or light primer strikes.

That’s why Redacted Arms uses an H3 as the starting point in its Super Safety kits. Some shooters run a carbine or H2 buffer successfully and only step up when they see problems; both approaches work if you test. Our guide to H2 vs H3 buffers for Super Safety setups covers the symptoms of each in detail.

AR-9 Buffer Weights

A 9mm AR-9 runs on straight blowback, so the bolt is held closed only by its own mass and the buffer. That’s why AR-9 buffers are much heavier than 5.56 buffers, usually about 5.5–11 oz depending on the maker and whether the rifle uses Glock-pattern or Colt-pattern magazines. A 5.56 H3 is usually too light for a 9mm carbine. Our breakdown of what makes the AR-9 platform different explains why buffer weight matters even more on blowback guns. Because magazine type and bolt weight change the timing, check the maker’s buffer recommendation for your specific lower and bolt before you buy.

How to Test a New Buffer Weight

1. Start with the buffer your gas system and barrel length suggest in the chart above.
2. Shoot at least two magazines of the ammo you use most, plus one magazine of the weakest load you plan to run.
3. Confirm the bolt locks back on an empty magazine every time.
4. Note where empty cases land and how the recoil feels.
5. If you see short-stroking or failures to lock back, go one step lighter. If ejection is far forward or recoil feels harsh, go one step heavier.
6. Change one part at a time, and retest after every change.

Signs Your Buffer Weight Is Wrong

• Ejection at 12–3 o’clock and heavy brass damage: overgassed; try a heavier buffer.
• Ejection at 4–6 o’clock, failure to lock back, or short-stroking: undergassed or buffer too heavy; try one step lighter.
• Dead trigger pulls on a reset device: the carrier is returning too fast; try a heavier buffer.
• Harsh, “bouncy” recoil: often too light for the gas system.

Ejection pattern is a useful clue but not proof; ammo, gas port size and spring condition all affect it. To see how weights scale across a full range of buffers from one maker, VLTOR’s A5 buffer specifications list each step from H0 to H4.

Common Buffer Mistakes to Avoid

• Buying by label alone. Two buffers both called “H2” can differ by more than half an ounce.
• Mixing systems. Carbine buffers belong in carbine tubes, rifle buffers in rifle tubes, and A5 buffers in A5 tubes.
• Fixing every problem with weight. If the gas port is oversized or the rifle is badly overgassed, a gas block adjustment usually works better.
• Ignoring the spring. A worn spring changes timing as much as a buffer swap.
• Skipping the function check. After any buffer change, confirm the rifle feeds, fires, ejects and locks back on an empty magazine before you trust it at the range or in a match.

Find the Right Buffer for Your Build

Use the buffer weight chart above as a starting point, then test with the ammo you shoot most. For a suppressed rifle or a reset-trigger build, the H3 is the safest place to start. Redacted Arms LLC offers the Super Safety FCG and H3 kit, which pairs the buffer with the parts it’s tuned for. Shop the kit, or contact our team if you’re not sure which buffer your build needs.