Whataya Mean My AR Already Has a Piston??

[MistWolf]

I'm starting this thread to keep from further derailing another.

When this was posted in another thread-


Your AK is your piston gun!

I'd sell the upper or whole AR and replace it with something of more quality. Like said above 2 guns are better than 1. Here's a thought, (going against the grain) Sell the AR and build up your amd-65.
Buy a krebs adaptor block and use AR stocks on it. I love mine since that mod. Either way I think everyone seems to agree that selling at least the upper/rifle would be a great idea.

I responded with-

The AR also has a piston

Which inspired-

You talking about one of the piston systems? Not a DI gun, right?

no, he's saying that the bolt/BCG in a normal DI AR is the piston/cylinder setup. The piston is just relocated. Don't think to hard about it. For all general purposes the AR is not considered a piston gun.

Oh ok one of those wise guys huh? J/k
:cool:
(Very astute. Too often I am one of those wise guys)


How can an AR have an operating piston and not be considered a piston system? Actually, how can the AR be a direct impingement system? What does the gas directly impinge on? What did Eugene Stoner identify the system as?

http://www.google.com/patents?id=ETJjAAAAEBAJ&printsec=abstract&zoom=4#v=onepage&q&f=false

I understand all of that and Im agreeing with you. I know the AR has a "piston". Most systems actually have a deticated piston not a piston that doubles as the bolt. and the gas impinges on the bolt.

Speaking generally about guns the AR is not consi

Are you all calling the gas key or bcg the piston? Don't pistons usually have rings?

Everybody up to speed? Good.

To answer TSH's last question, the tail of the bolt is the piston, complete with rings
http://i115.photobucket.com/albums/n289/SgtSongDog/AR%20Carbine/DSC_0114.jpg
If the rings are missing, damaged or worn, the rifle will not function. The bolt is the piston, the carrier is the cylinder. DI systems do not use rings, nor do they use an expansion chamber as the AR does. With a DI system, the gases impinge directly on the bolt carrier. If the AR gas key was just a cup, the AR would be a DI system. Instead, it's a tube guiding the gas into a cylinder.

For drawings of the Ljungman DI system and from the original Stoner patent, check out this thread
http://m4carbine.net/showthread.php?t=99050

This thread isn't about "DI vs Piston ARs". It's to clarify the fact that the AR has a piston and is not really a DI system.

This site is known to not accept simply regurgitating what others have posted on the internet. We are encouraged to do our own research and become our own Subject Matter Expert. I did my own research and discovered the AR isn't a DI system as is being often repeated. Don't take my word for it, do your own research of the AR, Ljungman and other operating systems and come to your own conclusions

[DeAdeYE15]

I've been following the "trade up" thread and was wondering were the piston comment was going to lead.

You make a good point, but I doubt it'll lead any one away from calling the AR a DI gun.

[M4Fundi]

I believe this below is a "true" DI system within a rifle, but since the AR's gas system is a hybrid of the DI and Piston systems should it have its own name, i.e. the Stoner Impingement Expansion Chamber Piston (sans rod) System or is there an accurate engineering term for the system that exists?

Is it important to differentiate between the the DI and the Stoner System this late in the game? It would take alot of reeducating and was wondering if there was anything to be gained or is it just for empirical clarification to give credit where credit is due for a unique system that is mislabeled as something inferior?

I enjoyed the post and like to see the clarity of facts, but was wondering if you were headed somewhere with it...

http://world.guns.ru/rifle/autoloading-rifles/swed/ag-42-ljungman-e.html

Would a Benelli M1 be considered a DI system? Haven't gutted one yet to find out...

[DeAdeYE15]

I think it's safe to say that it will stay labeled a DI system, since it has for 50+ years now.

[MistWolf]

Knowing the difference has given me a better understanding of how the AR (and other rifles) work and has lead me to asking and finding the answers to other questions. I also feel it will give folks a better understanding when discussing so-called "piston" uppers and when comparing the AR to other designs

[everyusernametaken]

Too often I am one of those wise guys

Sadly, some consider that to be a bad thing. Incidentally, those people are morons. ;)

I would call the DI architecture a "bolt-integral piston operating system". :D

[BufordTJustice]

From the patent (transcribed by me):

"It is a principal object of this invention to utilize the basic parts of an automatic rifle mechanism such as the bolt and bolt carrier to perform a double function. This double function consist of the bolt's primary function to lock the breech against the pressure of firing, and secondarily, to act as a stationary piston to actuate the automatic rifle mechanism. The primary function of the bolt carrier is to lock and unlock the bolt by rotating it and to carry it back and forth in the receiver. The secondary function of the bolt carrier is to act as a moveable cylinder to actuate the automatic rifle mechanism. By having the bolt carrier act as a moveable cylinder and the bolt act as a stationary piston, the need for conventional gas cylinder, piston and actuating rod assembly is eliminated.

It is an object of this invention to provide a gas system which is lighter and less expensive to produce because of its simplicity than the present gas system now used in automatic rifle mechanisms.

It is another object of this invention to utilize the energy of the expanding gas developed by the firing of the weapon for the actuating of the automatic rifle mechanism directly by use of a metered amount of gas coming from the barrel. This invention is a true expanding gas system instead of the conventional impinging gas system. By utilization of a metered amount of gas from the barrel, the automatic rifle mechanism is less sensitive to different firing pressures caused by variations in the propelling charge. It is therefore still another object of this invention, to provide a rifle mechanism which is not affected by variations in the propelling charge.

A further object of this invention is to provide smoother operation and longer life of the working parts of the automatic rifle mechanism. Since, in this invention, the actuating force is transmitted directly down the centerline of the barrel and the bolt mechanism to the shoulder of the shooter, all of the off center loads found in most other types of gas actuated weapons are eliminated."

-Eugene M. Stoner

http://www.google.com/patents?id=ETJjAAAAEBAJ&printsec=abstract&zoom=4#v=onepage&q&f=false (http://www.google.com/patents?id=ETJjAAAAEBAJ&printsec=abstract&zoom=4#v=onepage&q&f=false)

Mr. Stoner was a f*cking genius with his piston gun.

There, I did the bitch work for the forum.

I don't think Mist is trying to get people change what they call the AR system, but the very name is akin to the media calling it an "assault rifle". In the context of discussing piston AR models, maybe some people will realize that they have un-engineered and re-incorporated what Stoner took great care to remove. Further, the AR already HAS a piston, which also happens to be composed of the bolt and the carrier. Piston lovers will have their heads explode upon reading the patent text above. ;)

[TacticalSledgehammer]

I never thought of the rings on the bolt itself as piston rings. Mistwolf, you definitely have a good sense of "thinking outside the box" and now it makes sense to me. Starting this thread was a good idea.

[M4Fundi]

Yes, Mistwolf explains it well. Stoner was the one who was really thinking outside the box;)

[Clint]

Yep,
The AR has a co-axial piston integral with the bolt carrier.

[fixit69]

It makes some AR owners veins pop out when I bring this up. Thanks for the info, mistwolf.