Understanding AR-15 Buffer Weights
A wide variety of buffer weights and springs are available — from the cheap, mil-spec set that likely came with your rifle, to the high-end models that demand over $100.
Start to research the topic, and it’s easy to get lost in the potential benefits, drawbacks and recommendations.
But the best place to start is always a basic understanding of why they matter. Then we’ll take a look at the main types of buffer weights, what they’re used for, how to use them to optimize your rifle’s gas system.
Is the Buffer Really Important?
The buffer may look like a paperweight, but without one your rifle is effectively an awkward, single-shot rifle.
Every semi-automatic firearm requires the use of a recoil spring and buffer weight, which return the bolt carrier group (BCG) back into battery. Without a buffer in between it, buffer spring is made to be too strong to cycle the BCG, making the buffer essential.
But the movement of the weight helps absorb the already-minor recoil of the AR-rifle.
A heavier buffer takes longer to move, slows down more quickly and minimizes the ‘punch’ of the recoil while still maintaining the rifles function.
Having too much weight in the buffer can cause the rifle to short stroke, as the rifle’s gas system may not have the necessary power to cycle the heavier buffer (causing inconsistent extraction and ejection)
But having as much weight as possible increases the “dwell time” spent by the spent ammo in the upper receiver, allowing more of the excess gas and carbon to push out (cleaner operation).
More heat dissipates and there is more consistent extraction and ejection of the spent cartridge.
Getting the balance right can be affected by a fair amount of factors, including ammo types and calibers, proper installation of the gas block and tube, or the size of the gas port drilled into your barrel.
With that in mind, here’s an overview of buffer weight sizes and how they affect your rifle.
Carbine Buffer Weights (3 oz)
A standard buffer is made of an aluminum housing with three puck-shaped steel weights and three rubber washers to prevent the steel pucks from slapping directly into each other.
These buffers are designed for use in traditional carbine-length gas systems and with a wide range of ammo. They’re even more viable in mid-length systems, which place the gas block farther from the breach, lessening the amount of gas in the system and thus softening the impact of gas on the bolt.
Adjustment of this size of buffer housing, which is standard for most AR types, can be made by removing an end cap. This requires removing and replacing a roll pin.
Heavy (H1) Buffer (3.8 oz)
Heavy weights, or “H” weights, add about an ounce to the entire buffer. One of the approximately .6-oz. steel weights is removed and replaced with a tungsten weight, which is about 1.45 oz.
Adding even this amount of extra weight can cause issues on some rifles. But most AR-15s are over-gassed on purpose and can handle this type of addition.
H2 Buffer (4.6-4.7 oz)
The next rung on the ladder is the H2, which replaces two steel weights with a pair of tungsten weights, adding nearly two ounces to a stock buffer.
These heavy buffers can be too heavy for some carbine applications, though they are often used. An H2 is likely too heavy for many mid-length systems, but this is not where they are most often desired.
With the advent of AR-Pistols in recent years, shooters need heavy buffers to compensate. A standard carbine buffer is far too light and will likely result in violent cycling of the action.
H3 Buffer (5-5.4 oz.)
The H3 represents the heaviest of the carbine-length buffers for AR-pattern rifles, coming in at a hefty 5.2 oz., give or take.
Why have a buffer weighing fully two ounces over a standard buffer?
The single best advantage of the AR platform is the unbelievable versatility in calibers. In addition to the standard .223/5.56 chambering, AR-pattern rifles are found with heavier calibers such 7.62X39, .300 AAC, and some new offerings like the .204 Ruger and the .224 Valkyrie.
Above all of these are the monsters: the .458 SOCOM and the .50 Beowulf.
All of these heavy hitters are able to use a standard lower receiver assembly, but most of these systems are decidedly over-gassed. The impact of the gas charge of a .458 SOCOM with a muzzle energy of 2,700 ft. lbs. greatly exceeds that of .223 (1,200 ft. lbs).
The extra buffer weight helps compensate and dissolve that extra energy.
Pistol Caliber (5-8.5 oz.)
The heaviest buffers belong to the dedicated pistol-caliber AR platforms. These buffers often consist of a steel housing rather than aluminum and have a wide range of possible weights, often around 5 oz.
The rationale is that a direct blowback design applies more pressure directly to the BCG which slams into the buffer with no gas system to soften the blow, thus necessitating a considerably heavier buffer.
The secondary reasoning for a considerably heavier buffer for pistol caliber AR-pattern weapons is the nature of the weapons. There are a number of full-size, 16” pistol caliber carbines but an extremely popular alternative has been to go with pistol configurations.
Some manufacturers are making pistol barrels as short as 4” for AR platforms, coupled with short pistol-length buffer tubes making for a sharp blowback in the weapon.
Some of the heaviest in this category are HSS (6.5 oz.) and the XH buffer (8.5 oz).
Rifle-length Buffers (5 oz.)
One glance at a buffer from the A2 style fixed buttstock lets you know that it is a completely different animal.
The housing of rifle-length buffers are longer and designed to operate in the longer rifle length buffer tube — never in any carbine or pistol systems.
If it was used, it will slam into the end of the buffer tube, possibly cracking the lower receiver.
Considering the disparity in appearance alone, this can be an easy mishap to avoid.
But even so, it bears repeating: do not ever substitute one for other because they are never interchangeable.
If your rifle seems to work fine, and optimization seems unnecessary, the best advice may be to stick with what you’ve got.
Ultimately, it takes some experimentation to figure out which combination works best in your rifle, for your needs.
Added weight in the buffer can improve performance, and an H2 buffer with an extra steel and tungsten weight might give you the widest range of options to find the right balance.
One Last Tip
If there’s anyone that knows the AR-15 platform, it’s the US military. As a special offer for our readers, you can get the Official US Army Manual for AR-15/M4/M16 right now – for free. Click here to snag a copy.