What Are the Benefits of a Heavy Buffer?

Pistol-caliber Buffer

• Unlike the rifle-caliber ARs with their locked-breech design, 9mm and other pistol-caliber AR-15 variants do not fire from a locked bolt. Rather, the combined mass of the bolt and buffer is the only thing resisting the back-force of the cartridge. Because the bolt and buffer are much heavier than the bullet, the cartridge case does not leave the chamber until the bullet has exited the barrel. With "hot" loads the bolt cycling action can be rather violent, battering the internal components of the weapon and reducing its lifespan. A heavier buffer absorbs more energy and makes the carbine last longer.

Standard Buffers

• The standard buffer in both the rifle and carbine are steel. In the rifle, this is not a problem because the buffer is long enough to give it a weight of 5.2 ounces. When combined with the 20-inch barrel, this is sufficient. The rifle barrel has its gas port, where it receives a small amount of pressurized gas to open the bolt, out near the end of the barrel where the pressure has dropped considerably.

  The carbine has a much shorter barrel, so the gas port is farther back. This results in higher gas pressure entering the action, which causes a quicker, more violent operation than the standard rifle. The carbine also has a shorter buffer tube to provide space for the collapsible stock. This shorter buffer tube necessitates a shorter buffer that only weighs 2.9 ounces, which compounds the problem.

Heavy Buffers For Slower Cycling

• AR-15 manufacturers designed the H (heavy) buffer at 3.7 ounces, the H2 buffer at 4.5 ounces and the H3 buffer at 5.4 ounces. These buffers have internal tungsten weights to increase their mass. Notice only the H3 is heavier than the standard rifle buffer. The increased gas pressure of the carbine makes the bolt move much faster than it does in the rifle, and this can cause the spent cartridge to fail to eject. This creates a jam, which the shooter must clear before resuming fire. Anything you can do to slow the bolt will increase reliability; a heavier buffer does just that.

Improved Feed Reliability

• Another problem too-fast cycling can create is when the bolt fails to strip a new cartridge from the magazine. This can happen either of two ways: the bolt can jump over the cartridge because it is moving too fast, or it can cease forward movement due to friction when it contacts the cartridge. The heavy buffer slows the bolt to it is less likely to jump the cartridge, and the increased mass gives the bolt more momemtum to overcome the friction of the cartridge in the magazine.