When you’re first building out your AR, you’re usually focused on what optics to throw on there, furniture, muzzle devices, and maybe even a nice Geissele drop-in trigger. However, what often is overlooked when improving an AR-15 is the buffer system, more specifically the buffer and spring themselves. Buffers are fairly customizable and have the potential to vastly improve (or degrade) the performance of a rifle depending on the weights used.

What are Buffer Weights?

Buffer weights are small, circular weights that live inside your buffer tube. They’re the things you hear rattling around when you shake it, and generally help dictate how slowly or quickly your bolt goes back into the firing position, as well as the amount of mass that is being pushed against when your rifle’s bolt carrier group while it cycles.

When a round is fired within the chamber of an AR-15, the gas from the barrel is fed from the gas block and back through the gas tube into the gas key of the bolt carrier group (BCG for short), which launches the BCG into the buffer tube. The ‘buffer weight’ being a literal buffer between your BCG and your buffer spring, depending on the amount of weight it slows down the violent back and forth action as your BCG continually goes in and out of battery.

Why Do Buffer Weights Matter?

Your buffer provides two very important things: a surface area for your BCG to interact with, as well as a counter mass to push back against the BCG when it slams into it. It’s yet another part of a gun that operates on Newton’s 3rd Law.

Buffer Weights are important for a couple key reasons, all of them having to do with your gun cycling. First, buffers provide the proper counter-mass for the rifle’s gas system, and if weighted improperly can cause cycling issues such as short-stroking or if there’s too little weight, your rifle’s felt recoil will increase significantly and the internal parts will wear much more quickly due to the excessive force (otherwise known as “overgassing”).

Second, without a surface for your BCG to interact with, your AR-15’s bolt carrier group would not be able to evenly distribute its rearward force as the buffer spring compresses. This in turn would likely not even allow the BCG to cycle, as there would be insufficient force for the spring to return the BCG. Also, the BCG could just get stuck in the buffer tube.

Different Kinds of Buffers and Weights

There’s actually a few different kinds of buffers with the most common being ‘Rifle’ and ‘Carbine’ buffers. The main difference between the two is size and length. Rifle buffers are meant to accommodate a longer buffer tube and spring. You’ll most often see these in fixed A2 style butt stocks, not unlike the original M16s. As for the shorter carbine buffers, these are what most people will use as their AR 15 buffer weight.

Carbine Buffer Weights

Moving onto buffer weights, the stock standard buffer weight set-up for an AR-15 is going to be a carbine buffer. Carbine buffers have 3 steel weights, weighing in at a total of 3 oz. This is fine for most applications, and allows compatibility for a good variety of ammunition. This is the standard AR 15 weight.

Next in terms of weight would be what’s known as an ‘H’ or “Heavy” buffer. An H buffer is simply a carbine buffer with the exception of 2 steel weights and one tungsten buffer weight. Tungsten, since it naturally has more density than steel, is much heavier when it has the same volume. This is how weight is typically added to buffers. H buffers are a great place to start when you're initially trying to figure out how much more weight should be added to your system. H buffers are widely used and have a history of being very reliable.

If your H buffer isn’t performing as well as you had hoped, next would be the ‘H2’ buffer. An H2 buffer has 1 steel, and 2 tungsten buffer weights. This is where the ‘2’ is derived from, as you may have guessed already. The H2 buffer is best applied in rifles with shorter barrels and gas systems, or AR-15s chambered in larger cartridges, or in AR Pistol builds, as they require much more weight to cycle reliably.

On the much heavier end of the spectrum are H3 buffers, which consist of 3 tungsten buffer weights. An H3 buffer is normally reserved for rifles with very short gas systems, or AR-15s chambered in .30 caliber cartridges, such as 7.62x39 and .300 AAC. It is also recommended to use an H3 buffer with .50 Beowulf and .458 SOCOM, as these cartridges carry a lot of mass and powder.

Pistol Buffer Weights

Lastly are pistol buffers, which are among some of the heaviest buffers sold for AR-15s. Pistol buffers are usually much heavier than even H3 buffers, sitting at about 8 oz. at the heavier end. The reason these buffers are so much heavier is due to the fact that most AR pistol systems (as in caliber, not length) have a much heavier bolt, and operate on a direct blow-back system as opposed to standard direct impingement. Naturally, as there’s more force pushing on the buffer system, a heavier weight is needed.

Other Buffer Weights

In spite of the variety of standard options available, there are more exotic buffers and weight systems available for the more technically savvy. Be advised that this can get expensive very quickly, but the performance benefits out-weigh the price of entry for a lot of people:

Spike’s Tactical Intermediate Weights

Spike’s Tactical makes a great alternative for people who think that the standard weights for an H1 buffer, H2 buffer, or H3 buffer are just a little too heavy or too light .These buffer weights sit in between all of these H buffers in the ‘Goldilocks Zone’ for many people.

Odin Works Adjustable Buffer

Odin works offers an adjustable carbine buffer shell that comes standard with 3 Aluminum, 3 Steel, and 1 Tungsten buffer weight for shooters who really want to fine tune their AR 15 buffer weight.

LANTAC Adjustable Buffer System

Lantac’s Adjustable Buffer System (ABS for short) is a really interesting take on a buffer. It has an adjustable collar that allows the user to tighten or loosen the buffer tube spring based on personal preference. Unfortunately, the only way to get ahold of one of these would be through a private sale, or through buying one of Lantac’s Raven AR-15 rifles as they do not currently sell this buffer weight on its own.

What Buffer Weight Should I Choose?

The way AR-15s are set-up have a substantial influence over how much weight their buffer is going to hold, so naturally each separate rifle with its different combination of internal parts will need certain weights. How to determine which rifles need more or less less weight can be as easy as looking at them, and knowing what they’re chambered in. So what do heavier buffers do?

Heavier bullets or powder-loads are going to require heavier buffers, like tungsten buffer weights found in H2 buffer kits and H3 buffer kits, and shorter barrels also require heavier buffer weights. Most AR guys swear by H1 and H2 buffer weights, as they noticeably improve the shooter’s ability to control recoil as soon as they are installed. Generally speaking, you won’t need an H3 unless you’re shooting an AR-10 but even with AR-15s you’ll want to pay attention not only what buffer weight you choose but what type of spring you pair with it as well. See Sprinco’s buffer spring guide to learn more.

Here’s a handy chart for a visual on what your rifle may need based on weights:

How Do I Know If I Have A Mil-Spec or Commercial Buffer Tube?

In other words, how do you know if your buffer tube is going to last and won't strip its own threads when installing it (slight exaggeration, but it can happen)? The crucial difference between commercial and mil-spec buffer tubes is the respective metals they are made from and their size dimensions. Mil-Spec tubes are made from 7076 aluminum and the diameter of the buffer tube is smaller than a commercial one but the tube is also wider. Commercial buffer tubes are made from 6061 T6 billet aluminum, have slightly smaller internal diameters, shorter threads and a slanted back as opposed to a flat one on the mil-spec buffer tube.

Need a Buffer? We Got You Covered.

Whether you’re looking for lighter H1 buffer kits, heavier H3 buffer kits or anything in between we have everything you need to get yourself started on Modulus Arms. Check out our AR-15 parts!