[twosevenoneseven]

Can anyone that knows more than I do :dunno: about firearms explain the benefits of gas piston operated ARs vs. gas operated ARs. I have read that the "fix" (gas pistons) has been around for awhile, most notably for the M16 variants. However, I am curious that if this "fix" is so great, why is any recently produced AR made without a gas piston? Is it cost, recoil, maintenance, all the above?

Thanks.

 

[GeneticsDave]

James over at FBMG is the man to talk to, give him a call or go down there and have him explain it - it's worth your time.

 

[twosevenoneseven]

I was hoping for an answer on the board. Perhaps someone else has the same question.

 

[Guest]

I have the LMT piston system for their MRP. It was fun to tinker with it, took it out shot a few magazines then removed it (it was free so I satisfied my obligation to try it). I have also played with someone Else's bushmaster piston also a fun novelty.

In terms of how a gas operated firearm should function the Stoner gas system is about perfect. All moving mass and recoil are in a straight line, nothing above nothing below the bore line. Shot to shot nothing is faster than an AR. Gas Impingement also features relatively few parts. Fewer parts in a firearm is often considered a good thing.

Piston guns are cleaner, that is about the only advantage they have. The crap about the bolt carrier not getting hot with a piston system is meaningless. A cool Bolt carrier may result in your lube sticking around longer if it is prone to evaporation but the bolt carrier never gets that hot anyway (I shoot full auto all the time, I should know). With a piston system there is mass moving above the bore line; more parts, and you cannot engage the bolt with the piston without applying angular tension on the bolt carrier which will cause wear to your receiver, receiver extension and bolt carrier (mostly your receiver as it is aluminum and your carrier is steel) and may result in binding especially when the wear is pronounced. Cleaner may result in more rounds down range before a stoppage from fouling or it may result in fewer down range due to failure of a piston component.

In my opinion there may, in a couple years, be a piston system that shakes down as a good reliable product and a fine purchase for those who hate to clean their rifles; but that hasn't happened yet.

As the AR15 has evolved from a combat weapon to a man-doll the level of garbage to slop on one, due to demand generated by people who would rather play dress up with their AR than shoot it, has gone wild.

This is something written by Tom Lyons on the subject; he knows far more than I.

It comes down to this:

Nothing is perfect.

The Stoner Gas System was designed to cure the many problems that are present in an overhead piston design, by moving the piston into the bolt carrier behind the bolt. And that's what it did.

This cured the piston problems, but there was an imperfection because there is carbon-laden gas going into the carrier. However, virtually ALL of the major problems present in overhead gas piston systems were CURED.

Since nothing is perfect, there is a choice here as to whether to return to the laundry-list of problems associated with an overhead piston system, or to accept the one small problem of the Stoner Gas System, which came along with the cure for overhead pistons.

Rarely will anyone argue against the statement that there is definitely an advantage to the Stoner System in the AR15, regarding accuracy and controllability. These are the strong points that came with moving the gas piston behind the bolt. The AR15 with Stoner System is the fastest shot-to-shot carbine available, and also the most accurate. In normal conditions, it has no peer in actual shooting performance as a combat carbine or rifle.

Most piston proponents will point to the "sand reliability test", where in the worst possible conditions for the weakness of the Stoner Gas System design, the AR15 fared about a half-percent more likely to have some form of stoppage, which is beyond the full ammo load of a soldier. Moot point, totally.

This is "all sizzle and no steak".
You MIGHT gain some infinitesimally small advantage in stoppages, IF you fire the gun without lubing for more than 300 rounds without stopping, in a sandblast cabinet, compared against the SCAR or latest XM8.
There is NO WAY that can be extrapolated to mean that any piston system that you slop into the gun will be any advantage. In some cases shown on some threads on this board, some piston conversions can't even make 1000 rounds before it mechanically breaks, which is ironic when you are buying it to get supposedly improved reliability.
And you will definitely lose accuracy and controllability in normal conditions, whether you want to admit it or not.
And you will pay a lot more money.
And you'll have unnecessary wear on other parts that people don't talk about, from stuff like carrier tilt.

Here's the facts. In almost every military trial on the globe over 40 years time, there has been nothing that could consistently beat the AR15 in an all-out head-to-head competition. And all the competitors have been overhead piston operated guns.
Even right up to this very moment, there is nothing that can beat an AR15 in all the necessary categories to win out. Nothing. Not the SCAR. Not the HK416. Not the XM8. Nothing.
You have to try to tilt the field in a direction which "weights" the one area of AR15 weakness(high round count sand-cabinet test), in order for ANYTHING else to beat it . And even then, when you do everything possible to put it at its most vulnerable disadvantage, you can only get a half-percent better IN ONE AREA, and THAT'S ALL. And it was CLEAR, that the major amount of stoppages for the AR15 were "stacked up" after everybody knew it was going to need lube after that round count, and it wasn't lubed, so there you go. If it was lubed on schedule, then it would have not even shown a disadvantage in that area.

Now, to be fair, everybody can buy what they want. It's a free country, and there are many nice guns out there.
It doesn't have to be "better than an AR" to be a very nice gun.
But, it seems that there are some who can't sit for that. They MUST find some reason that what "they want" is BETTER THAN AN AR. And that might be possible, but it hasn't happened yet. When it does, we'll all know about it.

Edit to add:

There is another advantage to a piston. Gas in the face which is especially troublesome if you shoot with a suppressor (which I do) but it can easily be cured with a PRI gas buster or about a nickles worth of silicon caulking.

 

[Crusader Smithy]

Ok, here is the short of it. Some of the manufacturers out there have gone away from true Mil-Spec. This causes reliability issues especially when dirty. A great way to solve those issues are to go to a piston opperated system. The other fix is to have a Mil-Spec weapon. So really the piston is to fix a quality control issue and not an inherant problem with the weapon itself.

 

[twosevenoneseven]

Thanks for the explanation. Everything that I have read has painted the gas piston as the “golden boy” AR “fix.” The interesting thing is that there is no active marketing argument (that I have found) in favor of gas operation other than the fact that gas operated ARs dominate the market.

My interest in the debate was peaked after I had read about HK’s efforts to win the US military contract that would have phased out the Colt. As I remember HK was unsuccessful. And the article seemed to imply that the reason Colt kept the contract was a result of cronyism since the HK was clearly a “superior” system. After all not only was the HK416 the cleaner gas piston system, it was highly favored by SOGs.

 

[Crusader Smithy]

As long as your rifle is reliable the HK is not superior. You break away from the specs and your tollerences are all messed up and reliability goes down the toilet.

 

[fnfnc64]

I'm an AR junky. I love the things, and put Gene Stoner right up there (almost) with John Moses. Nothing is more user friendly. A couple years ago I purchased a POF gas piston upper and stuck it on an RRA lower. It is a very cool gun, I like it a lot.
But to be honest, I don’t think the added cost is worth the benefits.
Stoner’s gas system has taken a lot of verbal abuse over the years, but the things works. It gets dirty, so what? I clean my guns, so it has never been an issue with me. If you treat a gun right, take care and maintain it, it’s gonna work for you. If you get a good piston gun you are going to like it. I have been hearing good things about the LWRC stuff. But I don’t think a piston is necessary.
The one thing you do need to do if you get any AR is learn about the gun. I highly recommend FBMG’s armorers course. James does a good job teaching you all the basics.

POF is on the right

 

[Jeff Johnson]

...
Stoner’s gas system has taken a lot of verbal abuse over the years, but the things works. It gets dirty, so what? I clean my guns, so it has never been an issue with me. If you treat a gun right, take care and maintain it, it’s gonna work for you.
...

I've watched many episodes of History of the Gun on the History Channel ... one of my favorite series on that channel.

I found it interesting in one of these episodes that when the M16 was initially fielded in Viet Nam, the Army brass believed it didn't need to be cleaned, or so it would seem, because they didn't field cleaning kits with them as well. That proved to be a disaster and a rough initial impression for the gun to overcome. I wonder who decided that they didn't ever need cleaning? I doubt that it was Stoner. Maybe it was Robert McNamara or one of his so-called Whiz Kids. :dunno:

Once they fielded cleaning kits, the gun became very successful.

Of course, I'm speaking as an armchair warrior on this topic, since I gleaned this bit of knowledge from the comfort of my recliner.
I was never in the military. The Viet Nam war ended when I was about 16 years old.

 

[Crusader Smithy]

Once they fielded cleaning kits, the gun became very successful.

It was more than just that. They had extreemly tight tollerences at first. Tight enough that, even brand new and clean, one trip into the bush with the dirt, dust, and humidity and the weapon jammed after the first few rounds. I've read several accounts of the M16 being field tested on real patrols in Veitnam. Every one of them jammed and were useless without firing a full magazine. The only reason they made it out alive was the light machine gunner with his trusty M14. After that you bet they hatted the rifle and wanted their M14's back.
Of coarse the problem has been fixed since then.