Carbine Buffer: 3.0 ounces, (3) steel weights

The carbine buffer is best used with a mid-length gas system with a 16" barrel, in a traditional 5.56/.223 rifle setup. It may also be used with a carbine gas system, though felt recoil will be increased. Your AR-15 might feel "over-gassed" and punchy. If you're building an AR chambered in 300 Blackout, the carbine buffer should be used with subsonic ammo and a pistol-length gas system.

H Buffer: 3.8 ounces, (2) steel (1) tungsten

We like to call the Heavy, or "H", buffer the diagnostic buffer. It's what many shooters turn to if they're running a carbine buffer and their rifle's over-gassed, felt recoil is excessive, or the bolt unlocks too soon because the buffer's too light. The heavy buffer is also best used with a carbine or mid-length gas system in a standard 5.56/.223 rifle. It may also be used in a subsonic 300 Blackout gun equipped with a pistol gas system.

H2 Buffer: 4.7 ounces, (2) steel, (2) tungsten

The H2 buffer is usually the best buffer for a carbine gas system in a 16" rifle, cycling reliably with the least recoil possible. Most shooters report it works just fine with a mid-length setup, too. If You're Building An AR Pistol with a pistol-length gas system, you will want to stick with an H2 over an H or carbine buffer, though felt recoil may be high. The H2 buffer may fail to fully cycle in a rifle made to shoot subsonic 300 blackout, even with a pistol gas system equipped.

H3 Buffer: 5.0 ounces, (3) tungsten weights

The H3 buffer largely foregoes use in a standard 16"-barreled AR, and is instead typically used for 9" to 11" AR pistol builds running conventional 5.56 or .223 with a pistol-length gas system. Most shooters agree an H3 buffer is the minimum weight required to ensure your pistol doesn't feel punchy with excess recoil. Lastly, the H3 buffer is also frequently used in lieu of a conventional 9mm buffer for AR9 Builds, Which Rely On Blow-Back To Drive The Bolt, as its buffer weight is similar. This produces even greater recoil energy inside the smaller 9mm BCG, requiring greater weight.

Important Note: AR9 bolt carrier groups are physically shorter than the AR-15's BCG. While the AR9 operates using an AR-15 buffer tube and spring, the shorter BCG means it will over-travel past the bolt catch with a typical AR-15-length buffer. Many shooter install spacers (with a total length of 0.76" to 0.875") behind the recoil spring to compensate for this over-travel. You can even stack U.S. quarters in the back of the tube in a pinch.

HSS Buffer: 6.5 ounces, custom weights

Just as the H2 buffer is meant to dampen recoil and energy over a carbine buffer in a punchy 5.56 rifle, the HSS buffer is intended to tame the AR9s that still feel over-gassed when using an H3 or by-design 9mm buffer. The HSS buffer uses custom weights (though still usually tungsten) with a stainless steel housing to add even more weight.

XH Buffer: 8.5 ounces, (5) steel, (1) spacer

The big-boy XH buffer is mostly used in high-energy 9mm AR pistols running +P ammo, or .308- and 6.5 Creedmoor-chambered rifles. At 8.5 ounces it weighs nearly three times that of a standard carbine buffer, making it unreliable in most 5.56 and .223 guns. Some shooters do run an XH buffer in 5.56 and .223 pistols, though this is most often because the pistol in question is using a large-diameter gas port.