Stoner AR Operating System Technical Detail

[HansTheHobbit]

The AR rifle is indeed a 'piston' design ... I wish Stoner had named it as a 'coaxial piston' arm or 'direct impinged piston' arm or such, as the bolt itself is indeed a piston. The impinged thrust acts upon the gas rings.

Sadly, as a machinist & engineer, I'll opine (and probably offend others) by stating that anyone who falsely believes otherwise cannot read or understand patents, engineering drawings and/or physics :roll eyes

So tell me why the gas key on the AG42 isn't also a piston.

[Koshinn]

This is one of the strangest conversations I've ever had. Part of me wonders if you're just trying to derail the topic for your own entertainment. I don't know who told you that the AR isn't DI, but they were operating from a horribly flawed understanding of what constitutes a piston. Just because gas is involved doesn't mean something is piston operated, at least in the realm of firearms.

I bet you call a magazine a clip too?

Arguing about if an AR is a DI (common convention, everyone knows what you're talking about, but is incorrect) or Piston (no one knows what you're talking about, but is technically correct), is similar to clips (everyone knows what you're talking about, but is incorrect) vs magazines (fewer people know what you're talking about, is technically correct).

[HansTheHobbit]

I bet you call a magazine a clip too?

Arguing about if an AR is a DI (common convention, everyone knows what you're talking about, but is incorrect) or Piston (no one knows what you're talking about, but is technically correct), is similar to clips (everyone knows what you're talking about, but is incorrect) vs magazines (fewer people know what you're talking about, is technically correct).

No, I call it a magazine because that's the correct term. Look, I don't know where this idea came from that an AR isn't a DI gun, but it's wrong. If an AR isn't DI, then DI doesn't exist. And just because the bolt has gas rings doesn't make it a piston. The movement of the bolt is caused by the carrier, and then by direct blowback after it is unlocked. At no time does the bolt act as a piston. Again, a piston is a moving part, it's movement is directly caused by an expansion of gas, and it does work on other moving parts.

With the Hakim, you could argue that in some strangely philosophical way it's a piston gun. The gas key is functionally a very short long stroke piston. But anyone with a lick of common sense can see that it's really just part of the carrier, so it's a DI gun because there's nothing substantial that moves between the carrier and where the gas comes from.

Again, the definition of DI is any gun in which the gas is piped directly to the carrier without a piston in between. You can get all philosophical about what constitutes a piston if you want, but you can't get away from the definition of DI. Just out of morbid curiosity, what is your definition of DI???

[Berserkr556]

No, I call it a magazine because that's the correct term. Look, I don't know where this idea came from that an AR isn't a DI gun, but it's wrong. If an AR isn't DI, then DI doesn't exist. And just because the bolt has gas rings doesn't make it a piston. The movement of the bolt is caused by the carrier, and then by direct blowback after it is unlocked. At no time does the bolt act as a piston. Again, a piston is a moving part, it's movement is directly caused by an expansion of gas, and it does work on other moving parts.

With the Hakim, you could argue that in some strangely philosophical way it's a piston gun. The gas key is functionally a very short long stroke piston. But anyone with a lick of common sense can see that it's really just part of the carrier, so it's a DI gun because there's nothing substantial that moves between the carrier and where the gas comes from.

Again, the definition of DI is any gun in which the gas is piped directly to the carrier without a piston in between. You can get all philosophical about what constitutes a piston if you want, but you can't get away from the definition of DI. Just out of morbid curiosity, what is your definition of DI???

You're wrong. Calling the AR-15/M-16/M-4 Direct Impingement is incorrect. Look at Stoner's patent and other documents. Nowhere does he call it Direct Impingement but gas operated rifle. Sullivan & Fremont never called the operation DI either and they headed the design team. Direct Impingement is the French MAS-49 and Swedish Ag m/42. Your definition from Wikipedia is not a reliable source because anyone can write anything on the site. And yes the tail of the AR bolt is the piston and has been described as such by several of the men on the original design team. People are lazy and parrot what others say but it's incorrect to call the AR family DI

[HansTheHobbit]

You're wrong. Calling the AR-15/M-16/M-4 Direct Impingement is incorrect. Look at Stoner's patent and other documents. Nowhere does he call it Direct Impingement but gas operated rifle. Sullivan & Fremont never called the operation DI either and they headed the design team. Direct Impingement is the French MAS-49 and Swedish Ag m/42. Your definition from Wikipedia is not a reliable source because anyone can write anything on the site. And yes the tail of the AR bolt is the piston and has been described as such by several of the men on the original design team. People are lazy and parrot what others say but it's incorrect to call the AR family DI

DI is still a type of gas operated rifle, so it doesn't surprise me that Stoner used that term. So what is your definition of DI? I'm literally on the edge of my seat to hear that one.

You guys aren't even listening; you're just regurgitating the same opinions without anything to back them up. I don't know who started this thing, but they were wrong. ARs are DI guns by any meaningful definition of DI. That's why they've been called DI for as many years as I can remember.

[Clint]

Everyone commonly calls the AR system "DI", even though it technically isn't a true DI system like the MAS-49 and others.

They use a large diameter gas tube and "nozzle" to form a fixed piston that acts inside a "cup" (cylinder) in the bolt carrier.

This is very similar to the long stroke piston system used in the AK, except reversed.




To be fair, the AR system has characteristics of both conventional piston and true DI systems.

It has a piston and a gas tube.

In reality, all of these gas systems are pretty similar with the major factors being:
1) where the force is generated (gas block end or carrier end)
2) how the two ends are connected ( gas tube or op rod )
3) which piece moves ( piston or cylinder )

The AR is the only piston system to feature in-line forces, with notable mention of the various non-piston direct blowback, delayed blowback and short recoil/locked breech systems, which also feature in-line forces.

Below is the summary of Stoner's patent with a few items bolded for emphasis.

Hopefully we can put this to bed and get back on track with the original topic of severe usage endurance findings.

Sept. 6, 1960 -E. M. STONER GAS OPERATED BOLT AND CARRIER SYSTEM 2 Sheets-Sheet 1 Filed Aug. 14, 1956 II 2m \l ll Ill H in IMHM MI IWWHM IWH mH I k mm www em wk 8R.

1N VENTOR Eagelze M. Stone? mNE Y Sept. 1960 E. M. STONER 2,

GAS OPERATED BOLT AND CARRIER SYSTEM Filed Aug. 14, 1956 2 Sheets-Sheet 2 IN VENTOR Ezgerze M. Stazzer ATTORNEY GAS OPERATED BOLT AND CARRIER SYSTEM Eugene M. Stoner, Los Angeles, Calif., assignor to Fairchild Engine and Airplane Corporation, Hagerstown, Md., a corporation of Maryland Filed Aug. 14, 1956, Ser. No. 603,913

6 Claims. (Cl. 89-191) This invention pertains to automatic rifle mechanisms and in particular to the gas system employed for operating the bolt and bolt carrier.

The most widely used method of operation of automatic rifles today is the conventional gas cylinder, piston and actuating rod assembly; the only other system now in production use being the recoil actuating system. The blow-back or inertia block system is usually reserved for weapons using lower powered ammunition, such as pistol and .22 caliber weapons.

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 consists of the bolts primary function to lock the breach 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 movable cylinder to actuate the automatic rifle mechanism.

By having the bolt carrier act as a movable cylinder and the bolt act as a stationary piston, the need for a 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 systems 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 actuating the automatic rifle mechanism directly by use of a metered amount of the 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 center line of the barrel and the bolt mechanism to the shoulder of the shooter, all of the of]? center loads found in most other types of gas actuated Weapons are eliminated. It will therefore be obvious because of this factor that another object of this invention is to cut down on climb which occurs during automatic firing operations.

[HansTheHobbit]

Hopefully we can put this to bed and get back on track with the original topic of severe usage endurance findings.

Yes, hopefully we can. But just so everyone knows, I will continue to refer to ARs as a DI system, and it's up to them whether they want to argue that, and up to forum whether they want to entertain such shenanigans. I read the patent application, and it's obvious that they were simply trying to differentiate their design from previous ones, hence their use of terms like "stationary piston." I am of course willing to say that the AR is a unique type of DI that is original to Stoner, but it has far less semblance to piston operated guns than even other DI guns, such as the Hakim. So for the sake of clarity, can we please just continue to use the conventional terminology?

The case is the combustion chamber. The bullet is the piston

No.

[HansTheHobbit]

Thanks for at least taking the time to read up, but seriously - another chance to elicit direct feedback from somebody with insight about what does and doesn't work on weapons that get fired more than all but a few competitive shooters and DoD destined weapon system RDT&E folks will get to run - and now over a page has been wasted on semantics. This seems to be the curse on M4C - really good SME threads derailed by the new guy who assumes their experience trumps the combined value of google, other shooters on here, and SME's on here.

Oh blah blah yourself. I was trying to ask a meaningful question when everyone started humping my rump because I had the audacity to call an AR direct impingement. You DI reformists are the ones who derailed this whole thing, not me. Again, I don't know how this whole thing got started here, but you guys are operating on terrible information, and I'm not going to drink your koolaid no matter how much you brow beat me.

[thx997303]

You're a piece of work aren't you? A piston doesn't have to move to be a piston.

You're a lost cause. You're wrong. You can be wilfully ignorant if you want to. Next discussion.

So Ron, are the psa BCGs you've been running the premium BCGs?

[HansTheHobbit]

a sliding piece moved by or moving against fluid pressure which usually consists of a short cylindrical body fitting within a cylindrical chamber or vessel along which it moves back and forth

a disk or cylindrical part tightly fitting and moving within a cylinder, either to compress or move a fluid collected in the cylinder, as air or water, or to transform energy imparted by a fluid entering or expanding inside the cylinder, as compressed air, explosive gases, or steam, into a rectilinear motion usually transformed into rotary motion by means of a connecting rod.

A solid cylinder or disk that fits snugly into a larger cylinder and moves under fluid pressure, as in a reciprocating engine, or displaces or compresses fluids, as in pumps and compressors.

Yes, a piston has to move to be a piston, specifically under fluid pressure, i.e. the gas created by combustion. That's why it says "stationary piston" in the patent application. It's a made up term that was created for the sole purpose of describing their new system. You guys are reading way too much into it. The AR is a DI gun, everyone knows it, and it's never going to change.

Please let this be the end of it.