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AR-10 Buffer Weight Basics

5D Tactical - 9th May 2022

Everyone on the planet knows the name of the scary black rifle known as the AR-15. What people don’t often talk about is the older and much bigger brother the AR-10. In the early 1950’s, post WWII and the late days of the Korean War, the US government was looking for a lighter high-power rifle that was easier for the average soldier to carry. One that would allow rapid fire with the ability to carry more ammunition.

Eugene Stoner, the man behind the legendary AR platform heard the call and developed many styles of light rifles with synthetic stocks, finally nailing an amazingly functional futuristic looking rifle called the AR-10. This rifle shot the large 7.62x51mm NATO, commonly known as the .308.

Unfortunately, within a few years it was determined this beast of a rifle was still a little more than what the average fighting man of the time wanted to trudge through the swamplands of Vietnam with and the AR-15 won the contract. However, the AR-10 was not down and out, it still sees heavy use in civilian and military roles every day.

One fact that may not be as widely known is about the name AR-10 - We use AR-15 for every black rifle that shoots 5.56 or .300 BLK, but AR-10 is not every .308 style AR. Most that you see are actually .308 caliber rifles of different names like LR-308, AR308, PA10, REC-10, R-18, etc. AR-10 is only for the Armalite production rifles and have slight differences from the average .308 caliber rifle. For the purposes of not adding to confusion, we’re going to stick with the AR-10 naming throughout.

AR-10 Buffer Tubes and Recoil Springs

As many of you have likely found out the hard way, not all rifles are made exactly the same. There are two types of component sizes, mil-spec and commercial. If you have a commercial sized buffer tube, you’ll notice the moment you try to replace your buttstock that its slightly larger. Remember, commercial means bigger/robust, but mil-spec is more common, and they are not interchangeable.

For the sake of simplicity, lets discuss mil-spec. An AR-10 and AR-15 can see the same buffer tube, recoil spring, and buffer. Though not all rifles are built the same and with gassing and functionality with different ammunition charges, a standard AR-15 buffer might not cut it. It may not need to be said, but it's going to be, rifle and carbine buffers, buffer tubes and recoil springs are not the same. Depending on your rifle length you’ll need the proper one. Rifle is longer, carbine is shorter. The best way to know exactly what you have is to buy it all at once with an AR10 buffer tube kit. Getting an AR10 buffer tube kit gives you exactly what it sounds like, the buffer tube, buffer and recoil spring, all at the proper length for your firearm. With that in mind, let’s move on to AR10 buffer weights.

AR10 Buffer Weights

First thing is first. Know what you have. If your firearm is a rifle, the buffer tube is longer and to prevent malfunction, it needs a longer buffer. You’ve likely seen what a buffer looks like, pretty similar to a large nail with a hard rubbery cap at the end, if that cap isn’t long enough to travel through the tube during the cycle, you could eventually expect it to bind the recoil spring. The shaft of the buffer guides the spring through the cycle to keep it from binding. On the flip side, if your firearm is a carbine, it requires a short buffer since the longer rifle buffer can impede BCG travel in a carbine.

Thankfully, AR10 rifle buffer weights are relatively simple to remember, just use one that is made for a rifle, and you’ll be good to go. It's when you get to the carbines that things come with a few different numbers and tuning comes into play.

AR10 Extraction Pattern

Should you build a rifle that doesn’t have an adjustable gas block or won’t take one and you are experiencing extraction, ejection, or loading problems, the only way you may have without major replacement or gunsmithing is tuning in the buffer weight to what your rifle likes. The easiest way to know what effect your buffer weight has on the rifle is to look at the ejection pattern:

  • Think of your muzzle at 12 o’clock and the buttstock as 6 o’clock.
  • If the casings are flying out from the 12 to 3 o’clock positions, likely your firearm is over gassed with too light of a buffer.
  • From 3 to 4:30 (about a 45-degree angle from the ejection port) you’re good to go.
  • Any further back to about the 6 o’clock position, i.e. hitting you, your buffer may be too light or the rifle is leaking gas in which case it cannot fully eject the casing with the proper force and you’re soon going to experience feeding issues.
  • If you have anything but perfect ejection, the simplest and cheapest method of seeking a correction is to check your AR10 buffer weight, then try a heavier buffer. You can also try tuning the flow of the gas with an adjustable gas block or an adjustable gas tube (but not both). If the problem persists you should seek a reputable gunsmith.

Choosing an AR10 Buffer Weight

As we just discussed, if the rifle is functioning perfectly with a standard buffer, you may not want to play around with different weights and possibly get poor results. If it is anything other than perfect, there are 3 types of buffers to keep in mind.

The first type is always the standard or stock buffer. Nothing to change, they are the weight they were made to be, and you can’t add or take away, the standard for AR10 Buffer weights is between 3.8 to 5.4 ounces. “Stock” and “standard” can be a little misleading though. They are not all built the same. Standard for one company may be slightly heavier or lighter than another production AR10 buffer. Some are made with steel while others may be tungsten. Always check the specs, if you don’t want to deal with physical weights, buy a buffer that is made heavier or lighter than the one you already have.

The next type is the adjustable weight buffer. These are literally buffers with small weights that you can add or take away to tune your buffer to your rifle. There are a few companies that make them, but just for reference, something like the ODIN Works AR-10 Adjustable Buffer allows you complete control of the buffer weight.

Finally, the bougie option. There is such a beast as a completely captured buffer and spring assembly that drops into your buffer tube all in one shot. These are a little less known, but they greatly reduce that grinding sound and feel from the buffer tube that we all know and love in the midst of recoil. These come in standard and heavy weights, like the JP Enterprises Silent Captured Heavy Recoil Buffer Spring Assembly.

It's All in Your Hands

Choosing a buffer weight may sound tedious and unnecessary. Most people don’t care where their brass falls as long as the right part is going down range. This is true, but if you are putting the money into a precision rifle, you want it to last a lifetime and longer. One part, such as the buffer, that is even slightly out of tune with the rest of the rifle can take a drastic toll later on after multiple boxes are spent. If you can fix every problem with a simple pop-in part, why not right?

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Now that you have AR-10 rifles on your radar, get your next Black Anodized AR .308 Billet Lower receiver from 5D Tactical today and start sending rounds long range.