AR-15 Buffer Weight Calculator
Enter your gas system, barrel length, buffer tube and ammo, add a suppressor or a fast trigger, and get the buffer weight to start with plus the buffers in stock that match.
Quick answer
- A 16" barrel with carbine gas in a carbine tube starts with an H / H1 buffer (3.8 oz).
- Also common on this setup: Carbine (standard) and H2. 43 matching buffers are in stock in the GunPartPicker catalog.
Source: GunPartPicker catalog and build data, prices checked November 1, 2026.
What buffer weight do I need?
A starting point from the gas length, barrel length and what is hanging off the muzzle and the trigger. The ejection pattern on the range has the final word; the table further down reads it.
Stamped on the barrel or in the listing. Measured from the chamber to the gas port.
Dwell time after the gas port is what sets how hard the system runs.
Buffer length follows the tube. Only the weight is a choice.
Start with
H / H1
3.8 oz
Also common
Carbine (standard)
3.0 oz
Also common
H2
4.6 oz
Tube
Carbine
Carbine, H, H2 and H3 all fit
- A 16" carbine gas barrel is the classic M4 layout, and H is the mil-spec answer for it.
H / H1 buffers in stock
Matched on the buffer weight in the listing. A mil-spec carbine spring is assumed; if you run a stronger spring, go one step lighter on the buffer.
Ranked by what builders add most, in stock first. One listing per model.
Carbine (standard) and H2 buffers
One step either side of the starting point. Buy the one the ejection pattern asks for after the first range trip.
Ranked by what builders add most, in stock first. One listing per model.
AR-15 buffer weight chart: carbine, H, H2, H3, rifle and A5
| Buffer | Weight | Tube | Typical use |
|---|---|---|---|
| Carbine (standard) | 3.0 oz | Carbine | 16" mid-length, rifle gas in a carbine tube |
| H / H1 | 3.8 oz | Carbine | 16" and 14.5" carbine gas, the mil-spec M4 answer |
| H2 | 4.6 oz | Carbine | Short carbine and pistol gas, suppressed 16", fast triggers |
| H3 | 5.4 oz | Carbine | Suppressed short barrels, fast triggers on gassy guns |
| Rifle | 5.2 oz | Rifle | Fixed stock rifles, rifle spring |
| A5H0 | 3.8 oz | A5 | A5 tubes with a rifle spring; A5H2 is the common start |
| A5H1 | 4.6 oz | A5 | A5 tubes with a rifle spring; A5H2 is the common start |
| A5H2 | 5.4 oz | A5 | A5 tubes with a rifle spring; A5H2 is the common start |
| A5H3 | 6.1 oz | A5 | A5 tubes with a rifle spring; A5H2 is the common start |
| A5H4 | 7.0 oz | A5 | A5 tubes with a rifle spring; A5H2 is the common start |
| 9mm / PCC heavy | 5.5 oz | Carbine | 9mm blowback, the only thing slowing the bolt |
AR-15 ejection pattern chart: overgassed or undergassed
Stand behind the gun and watch where the brass lands. Twelve o'clock is straight ahead, three o'clock is straight out the ejection port.
| What you see | What it means | What to do |
|---|---|---|
| Brass at 1 to 2 o'clock, dented cases, sharp recoil | Overgassed. The carrier is moving too fast. | Go one buffer step heavier, or close an adjustable gas block. |
| Brass at 3 to 4 o'clock, consistent pile | Tuned. Leave it alone. | None. |
| Brass at 5 to 6 o'clock, weak ejection, no lock back on empty | Undergassed or overbuffered. | Go one step lighter, check the gas block alignment and gas key screws. |
| Runs fine suppressed, short strokes unsuppressed | Buffer is set for the can. | Adjustable gas block, or accept a lighter buffer and more gas to the face suppressed. |
How buffer weight tunes an AR-15 gas system
The gas system pushes the carrier back. The buffer and spring decide how fast it goes and how hard it comes home. More mass slows the carrier both directions, which gives the magazine more time to lift the next round, keeps the bolt from bouncing on lock up, and softens the recoil impulse you feel. Too much mass and the carrier does not travel far enough to lock the bolt back or strip a round.
Every variable in the calculator is a proxy for gas volume and dwell. Longer dwell after the gas port (short gas system on a long barrel) means more gas and a faster carrier. A suppressor adds back pressure. A fast trigger does not change the gas at all, but it needs the carrier slower so the trigger can reset ahead of it. An adjustable gas block is the one control that reduces the gas itself instead of fighting it with mass.
Frequently Asked Questions
What buffer should I run in a 16 inch carbine gas AR-15?
Start with an H buffer at 3.8 ounces. If brass lands at 1 or 2 o'clock, or you add a suppressor, go to H2.
What buffer should I run in a 16 inch mid-length?
A standard 3.0 ounce carbine buffer or an H. Mid-length gas on a 16 inch barrel is the softest common setup and rarely needs more.
What buffer does a 10.5 inch pistol gas barrel need?
H2 as the starting point. Pistol gas on a short barrel is heavily gassed. Suppressed, H3.
How much do the buffers weigh?
Carbine 3.0 oz, H 3.8 oz, H2 4.6 oz, H3 5.4 oz. The rifle buffer is about 5.2 oz and only fits a rifle length tube. VLTOR's A5 series runs from 3.8 oz (A5H0) to 6.1 oz (A5H3), with a 7.0 oz A5H4 to special order, in an A5 tube.
Can I run a rifle buffer in a carbine tube?
No. It is too long. Carbine, H, H2 and H3 buffers fit carbine tubes; the rifle buffer and rifle spring fit rifle tubes; A5 buffers fit A5 tubes.
What are the signs of an overgassed rifle?
Brass thrown forward to 1 or 2 o'clock, dented case mouths, sharp recoil and a bolt that bounces on the way home. Go one buffer step heavier or close an adjustable gas block.
What are the signs of an undergassed rifle?
Weak ejection at 5 or 6 o'clock, failures to lock back on an empty magazine and short stroking. Go one step lighter and check the gas block alignment and gas key screws.
Do binary and forced reset triggers need a heavier buffer?
Usually. A slower carrier gives the trigger time to reset and keeps the bolt from bouncing as the hammer falls. H2 or H3 is the common choice, and some makers sell heavier FRT buffers, but follow your trigger maker's instructions first.
Cite this tool: GunPartPicker, “AR-15 Buffer Weight Calculator”, https://gunpartpicker.net/tools/buffer-weight-calculator. Data from the GunPartPicker catalog and real community builds, prices checked November 1, 2026. Free to cite with attribution.
Read next
All guides →
More Gun Tools
- TuningBuffer System (3D)Watch an AR-15 cycle in slow motion, cut open: gas drives the bolt carrier back, the bolt unlocks and throws the brass, the buffer and spring soak it up and send it home. Swap carbine, H, H2 and H3 buffers, add gas or a suppressor, and see the carrier speed, where the brass lands and when it short strokes.
- LegalSBR Planner (3D)Set the barrel anywhere from 7.5 to 16 inches, put a stock, a brace or a folder on the back, pin a muzzle device or slide on a can. The ruler under the rifle shows whether you've cleared the 16 inch barrel line and the 26 inch overall line. Pick your state for its SBR, suppressor and assault weapon rules, then price every part and open the build in one click.
- CompatibilityFRT and Binary Trigger PickerChoose your platform and see every forced reset trigger, binary trigger and Super Safety the catalog carries for it, what the host needs to run one, and where each is in stock.
- LegalBarrel and Overall Length CheckerEnter barrel length, muzzle device and how the back end is configured, and see whether the build is a rifle, a short barreled rifle, a pistol or an AOW under federal law, with the barrels in stock at that length.
- LegalGun Travel CheckerCan I bring my gun to another state? Pick where you start, where you are going and what is coming along: carry pistol, AR-15, magazines, suppressor, SBR, brace, forced reset or binary trigger, hollow points. Every state on the route is checked for transporting firearms across state lines: magazine limits, assault weapon bans, NFA rules, carry permit type and trigger bans, with what to do before the state line.
- PlanningAR Build Cost CalculatorHow much does it cost to build an AR-15? Pick caliber, barrel length, stock or brace and optic, then drag both edges of the price band from the cheap end to the top end. Every slot fills with the part builders add most that is in stock, priced live. The headline total is the core rifle, optics and extras are priced separately, and beside them sits what builders really pay per slot, measured from real part picks. Roll a random build, or open yours in the builder in one click. Computed from over 1 million AR parts selected on GunPartPicker since 2020.
- CompatibilityMuzzle Thread CheckerPick your barrel's caliber and platform, get the standard thread pitch, and see every muzzle device and suppressor in the catalog that actually threads on, with live prices.
- CompatibilitySuppressor Mounts (3D)Put a can on its mount in 3D. Compare SilencerCo ASR, Dead Air KeyMo, SureFire Fast-Attach, HUXWRX QD, HUB 1.375x24 and direct thread: what goes on the barrel, what is on the can, how it locks and which cans fit which mounts. Cut it open to see the taper and the baffles, then shop the mounts and cans in stock.
- CompatibilityDI vs Piston (3D)Watch a direct impingement AR-15 and a gas piston HK416 fire in slow motion x-ray 3D. Follow the gas from the port back into the carrier, or into a piston that kicks an op rod, see which bolt runs hot, and compare weight, cleaning, suppressed use, carrier tilt and cost.
- CompatibilityUpper vs Lower Receiver (3D)Take a real AR-15 apart in 3D and see how the upper and lower receiver go together. Push the takedown pin, hinge the upper open on the pivot pin, pull the bolt carrier group and lift the upper off, with every part colored by the half it belongs to.
- CompatibilityHow Muzzle Devices Work (3D)Watch one shot leave an AR-15 muzzle in slow motion 3D through a bare barrel, a flash hider, a compensator, a muzzle brake and a linear comp. See where each sends the gas, and what that does to flash, recoil, muzzle rise and the blast beside you.
- CompatibilityHow a BCG Works (3D)Watch an AR-15 bolt carrier group unlock, extract and lock again in slow motion 3D, then take it apart part by part. See the cam pin turn the bolt out of the barrel extension, and what each part does.
- CompatibilityBuffer Tube and Stock (3D)See an AR-15 buffer tube, end plate, castle nut and stock go on in 3D, walk the stock through its six positions, and put a mil spec and a commercial tube side by side to see why a stock only fits one of them.
- CompatibilityHow a Charging Handle Works (3D)Watch an AR-15 charging handle unlatch and pull the bolt carrier back by its gas key in 3D, then watch the rifle fire while the handle stays put. Compare a standard latch with an ambidextrous one.
- CompatibilityHow the Gas System Works (3D)Watch a shot's gas go up an AR-15's gas port, through the gas block and back down the gas tube to the bolt carrier in slow motion 3D. Turn it down with an adjustable gas block, and see where the port sits on pistol, carbine, mid length and rifle gas.
- CompatibilityFree Float vs Drop In Handguard (3D)Watch an AR-15 free float handguard go on its barrel nut in 3D, lean on a free float and a drop in handguard to see which one moves the barrel, and lock an M-LOK rail section in. Plus M-LOK vs KeyMod and what length fits your barrel.
- CompatibilityHow Triggers Work (3D)Watch a standard trigger, a forced reset trigger and a binary trigger run inside an x-ray AR-15 in slow motion 3D. See the hammer, the disconnector, the FRT's locking bar and the bolt carrier at every step, and what each one needs and where it is legal.
- CompatibilityGlock Red Dot Fit CheckerPick how your Glock slide is cut and see which red dots mount directly, which need a plate, and the plates and optics in stock right now.
- CompatibilityGlock Size ComparisonPick any two Glocks and see them to scale as real photos sized to Glock's published dimensions, side by side, from behind and as an X-ray, with the difference in length, height, width and weight in one line and the pistols in stock for each.
- CompatibilityP385 Size ComparisonSee the SIG P385 CARRY, COMP and FULL to scale against the P365-XMACRO, the P320 and the Glock 19, 17, 45 and 43X, as real photos sized to the published length and height, with every dimension and where to order one.
- Paint plannerGun Paint PlannerRattle can guns online before you spray. Paint, stencil and camo a real photo of about 1,800 guns: AR-15s, AR-10s, AR-9s, AKs, every Glock, pistols, shotguns and bolt action rifles, the way the rattlecanned guns on r/rattlecannedguns are done, with Krylon, Rust-Oleum, Aluma-Hyde, DuraCoat and Cerakote colors, then get the cans to buy in spray order.
- TuningTwist Rate CalculatorPick a bullet and a twist rate, get the Miller stability factor, then see barrels with that twist and ammo loaded with that bullet, with today's price per round.
- TuningOptic Zero (3D)See where a 25, 36, 50, 100 or 200 yard zero hits on a 3D range, with your ammo, barrel length and optic height. Compare two zeros side by side, look through your red dot, EOTech or LPVO at each distance, then tap where your group hit and get the exact clicks up, down, left and right for your optic.
- PlanningNight VisionLook around a real 360 degree scene through Gen 1, Gen 2+, Gen 3 green and white phosphor tubes, digital night vision and thermal. Turn the moon down from full to overcast, switch on an IR light, compare two devices side by side. Or walk a 3D farm at night and spot the people, hogs and deer hiding in it. Then see the PVS-14, PVS-31, GPNVG-18 and the thermal scopes people buy, with prices.