Nalley Arms

Arming Pickens County Citizens

AR-15 buffers, overgassing, and other solutions

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Buffers; they are almost an afterthought. Most of us run a generic buffer and don’t even consider them when thinking about the function of a rifle. Why do they come in different weights, and when might you need a different buffer?

Let’s start with clues that indicate that you might need a different buffer:

Bolt not holding open. If your bolt doesn’t hold open after you exhaust a magazine, and it happens on more than one magazine, you might have a situation where you need a different buffer. Of course you want to ensure that it isn’t just a faulty magazine, but that’s relatively easy to eliminate as a cause.

Brass ejecting to the front. Normally, when a case is ejected, it will be to the 3 o’clock position or further to the rear. If you are seeing brass ejecting forward of that, it’s a good bet that more gas than expected is present and affecting the ejection.

Ejector chewing up the case rim; or failure to extract. Just like brass ejecting to the front rather than to the side or rear, if it looks like a small mammal has been chewing on the rim of your case where the extractor sits, or if the case fails to extract, and once you manually extract the cartridge, it looks like part of the case rim was ripped away, it’s likely the bolt began traveling rearward while pressure in the barrel and chamber remained high, and the case was pressurized against the walls of the chamber.

Recoil heavier than expected. This is the most subjective symptom, but if you’ve shot a number of similar rifles, and notice that you are getting more recoil than expected, it might be a situation where you need a heavier buffer, though absent any other issues, I wouldn’t jump to this conclusion solely on recoil.

For those of you with registered full-auto weapons, you might see symptoms like:

Bolt bounce: During full auto fire you find that a round is in the chamber, and the hammer is down, but doesn’t fire a round, you may be experiencing bolt bounce, where the bolt has cycled so fast that the hammer comes down before completely in battery.

Cyclic rate too high: If the cyclic rate seems too high, or you want to slow it down a bit, a heavier buffer may help you in that regard.

So why do these symptoms occur, and what is the problem in the first place? Generally speaking, it’s overgassing. Sometimes this can be precipitated by addition of a suppressor, or perhaps a different length barrel, or maybe it was just built that way.

Why

The AR-15 platform is a direct impingement system, meaning that a hole is bored into the barrel and, upon firing, routes gas back through a tube to actuate the bolt carrier. There are many choices of different barrel lengths, gas system lengths, and even size of the gas hole in the barrel, all of which can affect the gas system. That choice means that the days in which we would have only a single rifle and a carbine buffer are long gone.

The additional weight in heavier buffers increases the amount of gas needed to cycle the bolt carrier, which in turn increases dwell time. Of course there can be too much of a good thing, and it’s important to find the right solution. Contrary to popular belief there is no one magical buffer that will solve all over-gassing problems. This means working buffers up to find the point where your rifle functions appropriately.

But why is this a problem in the first place? Part of it is variability of parts, and ammunition. Manufacturers want reliability; or rather they don’t want a reputation for unreliability. Pushing more gas to actuate the rifle ensures that the rifle will function, even if there are a host of problems such as weak ammo, little or no lubrication, etc. But this ‘solution’ to reliability problems also has huge potential for causing overgassing.

There are a couple of other options to solve this problem, so lets talk about them:

Switching Bolt Carriers. If you are running an AR-15 bolt carrier, you can switch to a M-16 bolt carrier. The M-16 bolt carrier has more mass, and thus increases dwell time. Effectively this has the same effect as running a heavier buffer, though many people are already running M-16 bolt carriers.

Heavier buffer spring. Increasing the buffer spring rate can also help tame overgassing, perhaps in conjunction with a heavier buffer.

Adjustable Gas Block. This is the right solution to overgassing. It’s a little more involved than some of the other options – but it allows you to tailor the right amount of gas for your setup and dial it in. This means you can get the minimum wear and tear, minimum recoil, and maximum reliability. This isn’t practical for everyone, and it’s a bit more expensive than a buffer or spring.  The upside is that it actually solves the problem, rather than addressing the symptoms.

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This entry was posted on August 28, 2015 by .
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