Four Reasons Why the Operating Rod AR-15 Might be the Worst Gun Idea Ever

By CTD Blogger published on in Firearms

There’s a persistent line of thinking among certain circles in the shooting community that goes like this: Since many reliable firearms have an operating rod, replacing the direct impingement gas tube and bolt carrier group of the AR-15 will make it more reliable. This is a false equivalency, with its roots based on the old wives’ tale that direct impingement guns are inherently unreliable.

A semi-truck has 18 wheels designed to drive long distances. Wouldn’t it be awesome if your commuter car did too? Perhaps, but probably not. It’s the same way with AR-15s equipped with an operating rod. Here are four reasons why you’re almost always better off sticking to a high quality, direct impingement rifle:

  1. Operating rods tend to introduce more problems than they solve.

The AR-15 rifle is more complex than many shooters believe. There is far more to the function of the system than a simple “gas blows the bolt carrier back.” When the volume of gas heading toward the receiver enters the carrier key, it actually pressurizes the area adjacent to the gas rings.

BCM bolt carrier group

Starting with quality parts is the best way to get a reliable rifle. Not by adding the unneeded complexity of an operating rod.

This pushes the bolt forward, and keeps the entire assembly locked until pressures have dropped to a safe level and the brass case has contracted. If you remove this influx of gas by replacing the gas tube with an operating rod, you have a far more abrupt and violent system. The operating rod acts like a hammer, and bullies the bolt carrier group backwards in a most impolite fashion.

But that’s not the end of the piston-driven AR-15’s troubles. The battering ram-like rod forces the entire carrier down at an oblique angle, which causes “carrier tilt.” This tilt erodes the area of the receiver just in front of the buffer tube, and can cause major problems over time.

Furthermore, the additional reciprocating mass of an operating rod is much harder on gas blocks and bolt carrier groups, especially in simple conversion kits. Granted, many companies (such as LWRC) have perfected the overall system and removed most of the early problems. However, this comes at an added cost.

  1. The direct impingement design works just fine. Really.

…and if it doesn’t, something is wrong with how your rifle is built.
If you still think of a standard AR-15 as inherently unreliable, you need to get with the times. Properly built guns, such as anything from Bravo Company Manufacturing, Daniel Defense or FNH, USA will be as reliable as the day is long.

Arms makers like the ones above listed prove that the old, tired argument of “The direct impingement rifle defecates where it eats, and that’s bad!” just doesn’t hold water. But, you don’t have to spend over a grand just to get a reliable rife. Doing your research and purchasing reputable parts from the get-go will go a long way toward owning a bombproof gun.

Dirty AR-15 bolt

Here, we can see harmles carbon buildup on the tail of the bolt

As with any rifle (with or without an operating rod), proper maintenance is essential. Keeping both types of gun properly lubricated with a proven product such as FrogLube or M-Pro 7 is a requirement for stellar performance under all conditions.

  1. Spare parts.

In the extremely unlikely (read: impossible) failure of a standard gas tube on a semiautomatic rifle, a replacement can be readily found nearly anywhere gun gear is sold. That’s because the direct-impingement gun is the standard. Plus, it’s easy to keep one or more on hand very, very cost-effectively.

This isn’t the case with operating rod-based rifles. All parts are proprietary from manufacture to manufacturer, and are always more expensive than a simple gas tube or spare bolt and carrier. Plus, you’ll need multiple specialized parts just for one rifle to cover all of your bases. And good luck finding those spares if the world abruptly decides to end, and you need to bail out.

  1. Weight and complexity.

Rifles with an operating rod always add more weight and complexity to the overall gun, with few, if any, tangible benefits. In most cases, you’re better off sticking to the tried-and-true direct impingement methods.

Much can be said about light rifles, and doing everything possible to keep the overall weight down. If your rifle can be built without sacrificing reliability, why go with a heavier option? Adding comparative complexity with an operating rod is simply unneeded.

Even if it could be proven that an operating-rod equipped rifle was objectively more reliable than a properly built direct-impingent gun (and it hasn’t been proven), most users don’t shoot enough to have an actual need for the extra reliability.

AR-15 gas tube

This simple part is the key to the AR-15’s reputation for reliability

For the average shooter, a direct impingement gun is far more than good enough.

So, is that the end of the story with AR-15 operating rods?

All that being said, there is one area where an operating-rod driven AR-15 makes sense: With ultra-short barrels (10.5 inches and under, typically) and a suppressor. These unique conditions can cause issues for a direct impingement gun when used heavily, due to the greatly reduced dwell time of shorter barrels, and increased backpressure from use with a suppressor.

Rather than fundamentally changing the design of the AR-15 and adding multiple parts while introducing a new set of problems, simply set up your standard barrel length direct impingement gun for success, and shoot the snot out of it with quality ammo.

Do you have any first-hand experience with AR-15 reliability, in either piston or direct impingement formats? Tell us about it in the comment section.

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of Cheaper Than Dirt! Inc., its employees or management. Analysis performed within this article are only examples and for informational purposes intended to promote an open exchange of information. Publication of any assertions made within this article or analysis are solely those of the author and in no way should be construed to reflect the position or policy of Cheaper Than Dirt!


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Comments (170)

  • Phillip


    The gas key doesn’t vent gas, it simply meets the gas tube and lets it travel into the bolt carrier where the back pressure forces the bolt forward. The gas is actually vented out of the two holes behind the bolt that you see on a standard bolt carrier where the vast majority escapes, only a small amount actually remaining inside the gun and less making it into the receiver.


  • rlwieneke


    Why can’t we have an extended bolt carrier key that extends through the front of the receiver and into the handguard where it could vent the gas there instead of inside the receiver and it would still be gas impingement with none of the ill effects of a piston.


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