The versatility of the AR-15 rifle has made it the most popular weapon in America.  It’s easily and quickly adjustable, and the recoil is tame enough to be used by adults and children alike.  The ease with which the rifle can be modified also contributes greatly to its popularity.  

If you sell AR-15s today, you’ve instantly created repeat customers as they return time and again to buy parts and accessories to customize their rifles and make them their own. Most add-on items do not affect the rifle’s operation, but it is almost inevitable that these customers will also begin internal modifications. They will upgrade their bolt carrier group, change uppers to different calibers, and even change buffers and buffer springs in search of the most efficient combination possible. These modifications will eventually affect reliability, bringing customers back in search of a solution to their problem. 

One common problem is that the timing (or cycle rate) changes as modifications are made. The solution involves changing the buffer weight to correct this timing problem. These customers will come to you, so it’s crucial that you, as a salesman, understand what buffers are and how they work. Let’s take a quick look.

The AR rifle design operates on a direct impingement system, where a portion of the expanding gasses in the barrel are diverted to a gas block and tube. The gasses are transferred from the gas tube into a small piston chamber inside the bolt carrier group. This forces the bolt to push forward and rotate to unlock the bolt from the barrel lugs. Once the bolt is unlocked, expanding gasses in the barrel force the bolt to the rear, thus extracting and ejecting the spent casing from the chamber. The bolt carrier group travels to the rear, then reverses course to strip a fresh round from the magazine. It pushes the round into the chamber and locks the bolt into the barrel lugs, where it is ready to fire again. The forward movement is caused by the recoil spring in the buffer tube. You may have noticed that the buffer wasn’t mentioned, but it plays a significant role in the above operations.

The most common buffers for a carbine are the H, H1, H2, and H3 configurations. The difference between them is their weight. Manufacturers have extensively tested to determine the optimum buffer weight for each carbine or rifle configuration they sell. While several different ones may work, they have selected the one that will operate in most conditions where the carbine is likely to be used. Note: If the customer uses their gun as a duty weapon or as one for critical situations, they should stick with the factory combination to ensure reliability.  

How does the weight affect the carbine’s operation?

Changes in the buffer’s weight affect the bolt carrier group’s cycle rate, also known as the rifle’s timing.  Lighter buffers increase the BCG’s cycle rate. Heavier ones have the opposite effect and slow the BCG’s cycle rate. If the weight is too light or heavy, the rifle will begin experiencing cycling problems and become unreliable. Cycle rates can become faster than the cartridges can be fed from the magazine, resulting in an empty chamber. Cycle rates that are too slow may cause the BCG to have limited travel, where it may not go far enough to the rear to pick up another cartridge. You may have noticed that the rifle can end up with an empty chamber in either case.  

If the customer’s rifle begins having problems, there is a common (although unscientific) way to determine what’s happening. It involves observing where the ejected casings fall in relation to the ejection port. The best way to determine what is happening is by visualizing the rifle as centered on an imaginary clock where, when viewed from above, the barrel points at 12 o’clock and directly behind the stock is 6 o’clock. A properly timed rifle will eject casings anywhere from 3 to 4 o’clock. If they are ejected in front of that ideal zone, it is likely that the BCG is cycling too fast and needs a heavier buffer. If they fall behind the zone, the BCG is likely cycling too slowly and needs a lighter buffer.  

How is the weight changed?

If you remove the buffer from an AR and shake it, you’ll quickly realize that it’s hollow and has weights that move back and forth depending on the forces at play. Each buffer contains three weights and rubber washers that sit between them. Different combinations of materials are combined to vary the weight. Steel and tungsten are commonly used since tungsten weights are about twice as heavy as steel. It’s also possible to use aluminum weights. Here are the configurations for the most common buffer types:

H Buffer - Three Steel Weights

H1 Buffer - Two Steel and one Tungsten.

H2 Buffer - One Steel and two Tungsten. H3 Buffer - Three Tungsten.

Your customer doesn’t need to purchase one of each. A much easier route is available with a user-adjustable buffer such as the KAK or ODEN Works units. Both provide a main body and different weights that can be used inside them. The customer can then customize the weight based on their needs. The beauty of this is that as they continue to make modifications, they already have the needed items to keep up with the changes.

The buffer is just one piece of a system. It is one of many parts that affect a rifle’s timing. The goal of changing the buffer is to maintain a balance between all the involved parts. For example, the delicate balance can be disturbed if the customer swaps to uppers with longer barrels and gas tubes. The same can occur if a heavier barrel is used or the barrel’s gas port is larger or smaller. All these parts are intertwined. Changing one affects the others. People begin with buffers because they are the easiest and usually the cheapest way to affect the entire system. Most timing issues can be solved by simply swapping buffers as needed.

The most practical way to proceed is by determining the current buffer in the rifle and changing to the next lighter or heavier buffer weight as determined by the above testing procedure. If that’s not enough, take another incremental step. Most issues can be solved within this range. Continuing problems may indicate that a gunsmith or another experienced shooter should be consulted to determine if other system parts need to be changed.

This is part of the fun and frustration of owning and modifying an AR-type rifle. The range of accessories and modifications available is almost unlimited. But, one must understand how each component works within the total system to keep things working properly. Your understanding of how AR rifles work will help you solve your customers' problems. As a result, your customers will benefit and continue to make more changes. All of that equates to more sales and more satisfied customers.