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!

Tags:

Trackback from your site.

The mission of Cheaper Than Dirt!'s blog, "The Shooter's Log," is to provide information-not opinions-to our customers and the shooting community. We want you, our readers, to be able to make informed decisions. The information provided here does not represent the views of Cheaper Than Dirt!

Comments (167)

  • grant

    |

    Im tired of the misinformation that gets spread around. And sorry about the typos.

    1 Stoner did not design a direct impingement gun. His design was self described as an expanding gas system which does in fact utilize a piston. See that picture of a bolt? It HAS A PISTON INTEGRATED INTO IT!

    Direct impingement throws up fouling all over the breech face and chamber area, permitting excess carbon, corrosive materials, and mechanically corrosive action(the gases themselves with particulate moving at nearly supersonic speed) to affect the breech and chamber area of the gun. Causing increased wear, potential for stuck cases, and a generally dirty gun in this and the reciever area. A problem with direct blowback guns as well.

    The ar is little better, it initially diects gas behind the breech face, but it throws up every bit of that gas in to the reciever area behind the carrier. Which naturally finds its way forward, and fouling up the area it intitially avoided.

    Also, the gas pushes the piston forward, which though opposition causes the carrier to reciprocate, the carrier moving backward causes the bolt to rotate to unlock, allowing the bolt to travel rearward with the carrier. It you look into it, there is very little benefit to this design, other than a very mild reduction in pressures on the breech face, and a small reduction in recipratory forces, which btw can be another argument for unreliability and finicky action.

    2. The long stroke design does cause a tilting load on the carrier as it must be either mounted above the breech (AK) or below (garand) which can cause wear to the sheer loading surfaces of the gun (carrier/reciever rails) and with the AR that can be a problem because the carrier is made out of steel (neccessary) while it rides on aluminum load surfaces (stupid) thats why guns like the SIG556 were designed to be long stroke from inception use steel uppers at the expense of weight. I guess only mech engineers and metallurgists understand how crappy aluminum is. And how dissimilar metals should be avoided in shear load scenarios.

    3. The gun is lighter, and so is the bolt and carrier assy, but simpler? HELL NO! There are more parts and narrower gas passages taking a longer path through multiple parts. At least long or short stroke keeps all the expanding gasses forward of the action, taking a MUCH simpler and shorter path, venting quickly and reducing fouling in the gun. Is the AR simpler? No. More reliable ABSOLUTELY NOT easier to clean? Nope, harder.

    4. The gun is lighter because it uses less robust parts, these lighter assemblies and inferior materials under load make the gun more difficult to tune with a wide variety of loads and external factors such as humidity and ambient temperatures. Under optimum circumstances, there would be less felt recoil. Unfortunately we dont live in a sterile world.

    Also, the teeny bolt locking lugs on the ar upset me, they could and should be more robust, they probably wanted less rotation of the bolt to allow for quicker lockup and unlocking. But i see these as flimsy in an important area of the gun and more suceptible to sticking due to fouling.

    In summation. If you want a “simpler lighter gun” the vz58 is A simple gun which runs clean, is over a lb lighter than an akm, uses short stroke piston design. Shoots REALLY flat, and is robust in every way with fewer moving parts that are all made of STEEL! not to mention the .30 caliber round which is better for everything except punching paper. Guys, .223 aint a good round for anything else, its not even good at killing people. It is a “casualty producing round” it wounds well, not as good for killing (It doesnt “hunt”) and the short stubby light projectile has a poor ballistic coefficient compared to say, 5.45×39 or .220 swift. And it splatters at long ranges making it ineffective past say 300m? Dont get me wrong, there are alot of ppl and other creatures dead from .223, some at great ranges, but the same could be said of .22lr. Either way its irresponsible to hunt with a round like that. Even with the heavier, slower moving hunting rounds.

    IF you want AR ergonomics, and prefer .223, but dont want to sacrifice EVERYTHING ELSE, buy a SIG or a SCAR. Its a better gun. And you range queens wont mind the extra weight, you militia members, nut up and stop complaining about lugging around an extra lb or 2, do some pushups and cardio and increase ur strength while losing some of that gut.

    But im sure many will disagree

    Reply

    • Phillip

      |

      @Grant, the AR-15 is plenty simple in its stock configuration. If you find yourself perplexed at its design, you’re probably an idiot and would be better off peeling potatoes or cleaning the head. Pop some pins, pull out the bolt carrier, soak in CLP, scrub with toothbrush. Bam. Unless you’re engaging in thousand-round firefights regularly (extremely rare even for the people who get in firefights for a living) you will never have your weapon lock up on you from carbon and unburnt powder. It just doesn’t happen, and cleaning your weapon takes a total of 10 minutes. It doesn’t have to be polished to a chrome, it just has to be scrubbed and lubricated.

      Watch Iraqveteran8888’s AR-15 meltdown videos in which he tests both a DI AR and a piston AR and the results may surprise you. The DI AR-15 made it into the upper 700 rounds count before the barrel exploded, and that’s because it was made of 416R stainless steel, which sucks at handling heat compared to 4150 CMV. You may also be surprised to find that the piston AR he tested mushroomed at the operating rod, warped the bolt carrier and scratched the upper up. That’s 3 parts in need of replacement as opposed to 1 which had nothing to do with the operating system.

      The AR-15’s stock pseudo-direct impingement operating system is amazingly reliable, and if it were so fragile as you claim, tier one operators who get to pick and choose their gear wouldn’t still be using it to this day.

      The VZ58 is neither as modular nor as accurate as the AR-15 and uses a milled aluminum receiver, not “all steel”. It has a top-open action that allows an extreme ingress of filth and debris to enter the action, as opposed to the AR’s precision, tightly closed dimensions that prevent filth from entering IN THE FIRST PLACE.

      Your assessment of 5.56 displays an astounding level of ignorance. It’s perfectly adequate for killing people, has been for years. M855 was designed to penetrate a Soviet helmet at 1000 yards and is capable of exactly that, and produces a wicked wound channel which much greater velocity than your cherished 7.62x39mm. It was the effectiveness of the 5.56mm round that caused the Soviets to want to mimic its effects in the 5.45×39 which has a lesser ballistic coefficient, by the way. Are you among the school of dogma that believes 9mm to be inadequate, as well?

      Reply

    • Phillip

      |

      with, not which*

      Reply

    • Phillip

      |

      660 yards (600 meters) NOT 1000 yards. *

      Reply

    • Phillip

      |

      Form factor, not ballistic coefficient*

      Reply

  • Jim

    |

    A NATO study found shot placement is more important than caliber and recommends more range time in training.

    Reply

  • MCS Army vet

    |

    I have owned a Colt M4 Carbine for a good while now. Have put only a couple thousand rounds through it, all at the range, and have had zero FTL’s or FTF’s. Average session is about 200-250 rounds, green tip, soft point and plain ball rounds. It is dirty when I clean it but not near some described on these sights.
    Guess I’m lucky but I know the piece is built well.

    Reply

  • Jasper 32813

    |

    My experience with gas impingement tube on the AR 10 and 15 is growing.
    I have read many accounts about magazines causing cycling issues. I have always used magpul and see no need for change with them.
    One problem I do see that is another topic is bolt catch issues. There is without a doubt a blue print deviation problem between manufacturers. I can run them wet or dry the parts off and still have issues. Read some articles stating the holes for the springs of the bolt catch were too shallow and there seems to be some misunderstood tolerances that stem from the DPMS platform to the Aramlite platform. In any case it’s a pain.
    Enough of the bolt catch back on track.
    Gas impingement systems are fine. Have never had a doubt about it. They are a challenge for the hand loader. I do believe that hand loading rounds for these platforms will educate you as to what your rifle requires for correct cycling and accuracy. One persons load data for their rifle-barrel twist combo does not mean it will work in your rifle that very well may have the exact twist rate and barrel length.
    I started out with a Colt Light weight Carbine. 1:8 twist 16 inch barrel. I played around with all types of loads. 77 grain 80 grains so long you couldn’t load them in the magazine I tried all I could with this rifle and it made reloading an AR seem easy. I jumped in deeper and ordered a JP Enterprises. 223 Wylde. Now the Wylde is supposed to be a chamber that holds more pressure and I suppose it does. The first time in tried one of my tried and true loads suited for my Colt I got a refresher course on rifle cleaning. It spit a primer out and I was pissed. I spent all night cleaning this exotic piece. Don’t get me wrong. This is one nice rifle. I can set up at 200 yards and rapid fire into a 12 inch target and hit 20 out of 20 most times .
    This rifle just demands a lighter load with different powder to cycle properly. Less powder to make the same muzzle velocity equals less money saved.
    These rifles demand individual attention.

    Reply

  • Cliff

    |

    16 inch barrel, mid length gas system, H buffer, extra power buffer spring. Feeds all day with any ammo. ANd SMOOTH!!!

    Reply

    • Bob

      |

      I have an AR15 that I purchased in 1985. It has a direct gas system. I cound not get it to shoot more than 5 consecutive round at a time. I did everything I could think of. I am a Viet Nam vet and thought I knew about weapons especially AR15s. At the range one day I was having my usual trouble with feeding. The man next to me saw my troubles and ask if I would like to try a magazine from his rifle. The magazines were from Mag-Pul, all of mine were metal from the weapons manufacture. The Mag-Puls’ worked well and I had not even thought it might be a magazine problem. I use strictly Plastic magazines and run the rifle wet with oil. I have never had anymore problems of any kind. You’r never too old to learn.

      Reply

    • ss1

      |

      @Bob:

      Can you explain more about running it wet with oil? I have never done this before. Like are there any DO’s and DON’T’s?

      Reply

  • Jim

    |

    Re hk91. I’ve never been in combat but hard to imagine humping 20 pounds of rifle with five mags.

    Reply

    • US Army (retired)

      |

      The HK91 is about 10 pounds with a full magazine. Mine does a great job and NEVER fails to do what it is supposed to do. Yes 7.62×51 does weigh more than the 5.56 but I know I can trust it to put down whatever it hits. No need to worry about clean burning powder as it runs fine clean and filthy!

      Reply

  • Brent

    |

    Parts availability and weight are the only valid points made here. The d.i. design DOES crap where it eats and that’s a plain fact from the first one to the last one, at least the piston design gets the bugs wrung out (carrier tilt?….thing of the past.)

    What gets me is the attempt to focus on the failure of a gas tube as a problem pointed out by the piston community….it’s a stainless steel tube. It’s going to “function” i.e. crap where it eats until it jams, which it will do if not kept clean or run wet which is something that traditionally hasn’t been done. Now you need food grade lube because of the petroleum mist that’s going to be swirling around your head!

    Let’s not overlook the fact that these points of contention are like the 7.62mm vs 5.56mm AR argument, what people forget or just plain don’t know is that Eugene Stoner’s original design was in 7.62 and likewise he was working on the piston driven AR when the design was sold to Colt.

    Recent remote sustained firefights have proven (again) the weak point of the d.i. design but one couldn’t legitimately call the design a failure, it’s light, accurate, modular and serviceable in 90 out of 100 situations. All the cherry picking of negative points (or positive) of both designs to prop up one design in favor of the other is getting really tiresome. I have both, I shoot both and I am convinced that my LWRC piston driven 6.8mm spc is the epitome of the AR evolution but in a shtf nightmare scenario it would be foolish to run into a, defend the Republic/minuteman scenario with it when the military and police use the d.i. system like my Bushmaster M-4 in 5.56.

    Shoot what you like, like what you shoot and pray our service members are triumphant in combat regardless of what design they are defending our Republic with.

    Reply

  • Ron

    |

    There are better guns and operating systems out there, but let say you really have to go into battle, what gun are you more likely going to be able to pick up ammo and parts for in the field?

    Reply

    • US Army (retired)

      |

      As far as ammo, the .308/7.62 is a very common everywhere so I believe I’ll be good on that aspect. The HK-91 side of it, I make a habit of carrying the most common repair parts such as replacement rollers, a spare bolt assembly but not much else. The 91 is hard to beat!

      Reply

    • ss1

      |

      @US Army (retired):

      As you may remember, you already helped me with advice last week. But now I have more questions.

      Would you say that your HK-91 is closer to AK technology, or AR technology? My guess is AK.

      Can you please look up, here on Cheaper Than Dirt, the Century Arms C308? I like the price on this baby!! Is this patterned after your HK-91, or do you see significant differences? Even if you’re not a fan of Century Arms I would appreciate your comments.

      Here’s where I stand…..I’m blown away and shocked by all the drama and complications of AR’s that have been discussed on this forum. I’m tempted to sell my DPMS LR-308 AR-10 (most likely a DI system) and buy this Century Arms C308 and put cash in my pocket, knowing that I also bought into more reliable technology.

      Any opinions from anyone else would be appreciated. This is real dollars and cents for me. My gun budget is limited.

      Reply

    • US Army (retired)

      |

      Neither one, the HK and it’s predecessor the CETME operate on the delayed blowback roller locked system. Simply put the bolt is held in place after a round is fired by the two rollers that hold it in the locked position until the pressure has dropped to a safe level. The rollers unlock and the remaining gas pressure, assisted by flutes in the chamber which assist in “floating the spent casing and cause the bolt to move rearward ejecting the spent casing and picking up a new round. Is it dirty? YES! Is it more reliable that a DI system? YES! I have fired many rounds before cleaning mine but I have not had ANY malfunctions with my HK91. The Century Arms C308 is a good deal. Another upside is the availability of magazines at a VERY reasonable price. Aluminum mags go for about $2-4 per and steel mags for about $3-5 per. I personally have 40+ magazines, mostly 20 rounders but a couple of 10 round and a couple of 5 round mags. I hope this helps and if you are like me you will love shooting it. It just gobbles what you give it!

      Reply

    • ss1

      |

      @US Army (retired):

      Thanks for all the excellent info!!

      How would you rate the HK91 accuracy versus AK’s, and versus AR’s?

      I am SOLD ALREADY on either the C308 or C93. All I need to do is put 2 or 3 guns up for sale, and when 1 sells, I buy a C93 or C308 (I still need to decide which one).

      Thanks much for telling us about your HK91. That’s why I hang out here. I learn things and become aware of guns that I had no idea existed.

      Reply

    • US Army (retired)

      |

      Mine has an 18″ barrel, which I would recommend for the C308 (7.62). I don’t believe the C93 (5.56) is available with an 18″ barrel, not sure.

      My HK91 I used to drop a deer last year and paced it off at 300 yards. I aimed at the top of its shoulder and hit it about 2″ lower which broke the spine. It dropped right where it was standing. I have a rail for scopes and I used a Simmons 3-9x40mm standard hunting scope. I sighted it in to be dead on at 200 yards. I won’t shoot at a deer over 300 yards unless it is standing perfectly still. I also have a Ruger bolt action 308 and if I am hunting where there may be a need for more range I’ll use it due to the 22″ barrel.

      Reply

    • Secundius

      |

      @ US. Army (retired).

      The longest-barrel available for the HK93 (C93) is a 41V50 556 Match Grade Barrel of ~26-inches in length with a 1:9 Right Hand Twist…

      Reply

    • Secundius

      |

      @ US Army (retired).

      H&K has a 26-inch 1:9 RHT Match Grade 556 41V50 Steel Barrel if your Interested for about $499.99…

      Reply

  • Layke Tactical

    |

    Regardless of what make or model of gun you have, if you clean your gun after every outing it will give you a life time of service. I have never seen a properly maintained gun fail. If you think buying a piston gun will get you out of cleaning your gun it will fail too.

    Reply

    • US Army (retired)

      |

      I totally agree with your comment. I made some comments based on actual combat experience in Vietnam. The M-16 was not properly vetted, i.e. it was put into service as a front line weapon without the necessary testing and it cost good men their lives. I have had an aversion to it since. Yes the problems were resolved but I won’t but one. I’ll stick with my current delayed roller locked H91 clone. I am saving up to get an M1A, which is a operating rod weapon. I trained in the Army on it and when I was handed an M-16 I went to the troop armorer and swapped it out for an Ithaca 12 ga. riot shotgun. I was on a tank, I had no need for the M-16 but the shotgun was excellent if I had to dismount.

      Reply

    • Old Navy

      |

      I was in Vietnam for 2 tours in 1969-1971. I got a lot of trigger time and I never had a problem with the M-16. I preferred a Stoner, but the M-16 was just fine. I also liked the 12 gauge. If you are worried about reliability, I would just get an extra DI upper to slap on your lower. I have put tens of thousands of rounds through weapons with and without an operating rod. The only failures I ever encountered were of my own making.

      Reply

    • US Army (retired)

      |

      Old Navy, Welcome home brother! I was in Vietnam on my first tour (1969) and got injured due to an RPG about 5 months in. Spent time in/out of hospitals for nearly 8 months, finally got medically cleared and immediately got orders to go back. Arrived Aug, 1970 back to the same unit (3/5 Cav) and finished a 12 month tour. Got nicked by shrapnel two more times but nothing serious. Being on a tank I found the M-16 to be unnecessary. That is why I preferred the 12 gauge. I now own a HK-91 (7.62) that is probably as dirty firing as the M-16 but it is not DI. The beast will shoot whatever I feed it and clean up is very easy. Never has any FTF, FTE or other malfunctions. It IS VERY hard on the spent casings. I had a deflector spot welded on the ejection port and I can now reload my spent brass!

      Reply

Leave a comment

Your discussions, feedback and comments are welcome here as long as they are relevant and insightful. Please be respectful of others. We reserve the right to edit as appropriate, delete profane, harassing, abusive and spam comments or posts, and block repeat offenders. All comments are held for moderation and will appear after approval.

Time limit is exhausted. Please reload the CAPTCHA.

%d bloggers like this: