Short answer: a heavier buffer slows the bolt carrier and softens recoil, but too heavy can cause short-stroking. Match the buffer to your barrel length, gas system and ammo.
The common weights
Standard carbine buffers are the lightest. H, H2 and H3 add tungsten weights in steps, each heavier than the last, roughly from about 3 ounces up to about 5 ounces.
When to go heavier
Shorter gas systems and short barrels run harder and often like a heavier buffer. Suppressed builds also tend to cycle harder.
When to stay light
Long gas systems and some light loads can short-stroke with a heavy buffer. If it fails to eject or lock back, go lighter.
Match the spring
The buffer works with the action spring. Use parts made for your tube type.
Our buffer system compatibility guide covers the full set.
How to choose
- Standard carbine buffer: the usual choice for a carbine gas system.
- H, H2 and H3 buffers: heavier buffers slow the carrier and can reduce harsh cycling on short or overgassed rifles.
- Rifle-length buffers: for rifle-length buffer tubes and spring systems.
Signs your buffer may be wrong
- Failure to eject, or spent cases that land very close or far away.
- Failure to lock the bolt back on the last round.
- Harsh recoil or a sharp bolt return.
How to tune
Start with the buffer that matches your gas system. If the rifle cycles too hard, try a heavier buffer. If it short-strokes, try a lighter one. Change one thing at a time and test with the ammunition you use most.
Keep building
Browse AR-15 parts, read the custom AR-15 build guide, or let our Palmetto, FL shop help with gunsmithing and custom AR builds.
Shop AR-15 parts at BMTC USA, a gun shop and gunsmith in Palmetto, FL.