I'm not looking to argue with anyone here, I am just looking for references - This is not to decide whether I should go out and buy X or Y piston on the market or whether gas pistons or direct inpingement is better (Frankly, if I had the cash, right now I think I'd spend it on training and make me a better weapon).

I am looking for any link or reference (book, article, whatever) so I can go read Stoner's arguments.  I am not interested in more hearsay - I am looking to find primary and/or secondary source documents (either Stoner or Cadillac Gage preferably, or if someone can give me a title of a biography that did primary research and included references).  

My understanding is that early designs of his did use gas pistons but that he abandoned them.  I want to know why, and what limits caused it.  I want to know qualified references and not internet blabber.  I know the team here has considerable individual and collective knowledge, and I'd like to tap that knowledge to get to first hand/primary sources.

Again, this is academic and looking for references, not arguments.  I want a reference not an I heard from so-and-so or read somewhere that thinks gas pistons are good or bad - I want to know Stoner's reasons and Stoner's alone, or CG's responses to Stoner (or Mil or competitors analysis/responses to the designs/decisions).  I've got lots of attributions of facts on the good old web via Google and books, articles, etc, but cannot find hard references with facts to back them up, and most of the so-called Stoner biographies I keep reading are less than stellar on design decision information.  

* Bonus Q: Does anyone know Stoner's rationale for advising Cadillac Gage not to adapt the Stoner 63 for the XM235 (6x45mm)?  Is there a memo or anything referencing Stoner on this or is it all hearsay?

Tag.

I have wondered, since he made the AR15 direct impingement and the AR18 a piston system...

First off Stoner brought the gas design with him to ArmaLite, and then ArmaLite sold the then patented gas design to Colt's.  That is why Stoner's later designs incorporated pistons (such as the one he did at Cadillac Gage).

Once the patent was expired he went back to his gas system, ie the SR-25.

References:

The ArmaLite AR-10 by Maj. Sam Pikula, USAR
The Black Rifle by R. Blake Stevens and Edward C. Ezell

There were several rifles floating around in the 40's and 50's with direct gas systems.  Stoner's rifle was designed primarily for light weight, and a small metal tube certainly fit that bill over a clunky chunky gas piston.  His AR is really a great combination of immitation and innovation--as are all great engineering feats.

It is interesting that direct gas was never widely adopted outside of the AR family and a few knock-offs (Daewoo?).

Daewoo K200s are piston. The French Mas autoloader is apparently DI.

Not popular, anyway.

This is the (in)famous Ljungman gas system...



It is often attributed to the Frenchman,  Rossignol.  A similiar system is indeed used in the MAS-49.

It's not too awful close to what we see in the AR.

Quoted: This is the (in)famous Ljungman gas system... world.guns.ru/rifle/ag42patent.jpg It is often attributed to the Frenchman,  Rossignol.  A similiar system is indeed used in the MAS-49. It's not too awful close to what we see in the AR. As to the AR18, I don't know how much of a role Stoner played in that rifle.

Stoner had allready quit ArmaLite before the AR-18 was designed.  ArmaLite had to use a gas piston set up because they had allready sold Stoners gas system to Colt's.

In order to get "primary" information we would have to talk to Mr. Stoner himself.  Since he is no longer living we have to depend on second hand information.  

According to articles in the magazine Machine Gun News, during the 1950s Mr. Stoner was working on developing lightweight firearms using materials that were new to firearms construction such as aluminium and fiberglass having a knowledge of working with these materials in the aircraft industry.

At the time heavy steel receivers were needed to withstand the stresses that operating rod systems placed on the receiver.  Using aluminium receivers in his M5 and M6 designs resulted in cracks in the aluminium receivers when using an operating rod system.  He employed a direct gas system in his M8 design to overcome this problem.

Here is a picture of Mr. Stoner's first design (the M8) using a direct gas system.  The gas tube is actually on the left side of the rifle as can be seen in the close-up shot.  As stated above he had been working on this design before going to work for Armalite.

Those M8 pics are cool!

The best source may be Stoner's patent for the gas system.  While granted in 1960, the rifle shown is the AR-3.

US Patent #2,951,424 "Gas Operated Bolt and Carrier System."

Quoted: In order to get "primary" information we would have to talk to Mr. Stoner himself.  Since he is no longer living we have to depend on second hand information.   According to articles in the magazine Machine Gun News, during the 1950s Mr. Stoner was working on developing lightweight firearms using materials that were new to firearms construction such as aluminium and fiberglass having a knowledge of working with these materials in the aircraft industry. At the time heavy steel receivers were needed to withstand the stresses that operating rod systems placed on the receiver.  Using aluminium receivers in his M5 and M6 designs resulted in cracks in the aluminium receivers when using an operating rod system.  He employed a direct gas system in his M8 design to overcome this problem. Here is a picture of Mr. Stoner's first design (the M8) using a direct gas system.  The gas tube is actually on the left side of the rifle as can be seen in the close-up shot.  As stated above he had been working on this design before going to work for Armalite. home.comcast.net/~gocartmozart/stoner1.jpg home.comcast.net/~gocartmozart/stoner2.jpg

Great post, never heard the aluminum receiver cracking thing before.  Thanks for sharing the pictures.

Here it is in person (kinda).  Weight was the reason for direct gas.

Quoted: Here it is in person (kinda).  Weight was the reason for direct gas. i1.tinypic.com/nvtdz9.jpg

Not going to get a weight reduction with DI.  The weight is just in a different part.  Instead of a heavy op rod/gas piston you end up with a two piece bolt.  The added section of the bolt, the "carrier" has to be as heavy as the formally used op rod/gas piston set up.  The weight is needed in order to reliably open and close the bolt.  The weight ratio of the op rod/piston/carrier compared to the weight of the bolt is an important aspect to weapons design.

Also, notice that the gas piston set up Winchester trial weapon was lighter then it's competitor the AR-15.  The Ruger Mini-14 is also light, with a gas piston set up.

In addition both the Winchester trial weapon, and the Rugar Mini-14 used steel and wood, yet are as light or lighter then the AR-15.

Thanks for sharing the picture.

Quoted: Not going to get a weight reduction with DI.  The weight is just in a different part.  Instead of a heavy op rod/gas piston you end up with a two piece bolt.  The added section of the bolt, the "carrier" has to be as heavy as the formally used op rod/gas piston set up.  The weight is needed in order to reliably open and close the bolt.  The weight ratio of the op rod/piston/carrier compared to the weight of the bolt is an important aspect to weapons design.

This is just that internet optinion that the OP didn't want, but from an engineering perspective, DI does indeed make a weight reduction possible.  Putting the piston directly in-line with the bore allows the use of lighter parts (like using AL instead of steel for the receiver) by eliminating torquing loads and basically concentrating all of the forces involved into the bolt/BC, barrel extension and buffer tube.

Maybe metallurgy has advanced to the point where the forces of an offset piston are not a problem... I guess we'll see as the current crop of piston driven AR-15s get high round counts on them.

Is that an ACE stock on that AR-8?  

Mr. Stoner told me that he used the gas tube approach to meet the Army's light weight requirement.  Also why he used latest aircraft retractable landing gear manufacturing manufacturing technology such as machining out lightweight aluminum forgings.
Later, on the Stoner 63, he said he was not under such a severe weight limitation, and was designing to appeal to countries that had sheet metal stamping/welding type frabrication equipment/expertise.

Quoted: Mr. Stoner told me that he used the gas tube approach to meet the Army's light weight requirement.  Also why he used latest aircraft retractable landing gear manufacturing manufacturing technology such as machining out lightweight aluminum forgings.

EDIT:

Took out my comments and have added quotes.  

The late Col. C. H. Harrison is my favorite writer on the AR.  Unlike other writers, he was not a historian, or a big fan, he was the real deal with a history in Ordnance.  Wish we had guys that wrote like he did around today.

Considering Harrison's stature think this issue of weight is best put in perspective with direct quotes.  Here is what he had to say on the subject:

AMERICAN RIFLEMAN July 1958, page 18

At the request of the Continental Army Command in 1957, two .22 rifles for this development requirement were designed, and the first models of both became available in 1957. One is a product of the ArmaLite Division of Fairchild Engine and Airplane Corporation.  Called the AR-15.....Details of it's make-up have not been released by its maker for examination. The other rifle, product of Winchester-Western Division of Olin Mathieson Chemical Corporation, is called the Winchester Lightweight Military Rifle Caliber .224..... Weight of the Winchester Lightweight Military Rifle is 5.3 pounds with empty magazine.

AMERICAN RIFLEMAN June 1959, page 24

..........weight with empty magazine 5 lbs. 12 oz. However, the results  should not be overestimated merely because the means appear striking.  In the gas system, for example, elimination of the operating rod requires a bolt in 2 parts, with a cam surface between them corresponding to the operating rod cam.  Also, since moving parts of a certain mass are required for a given operating characteristics, elimination of the operating rod  requires a heavier bolt to keep the moving mass of parts up to that required.  So this construction does not reduce number of parts or working surfaces, nor essentially lesson weight.  Somewhat similarly, while aluminum is used extensively, the AR-15 weighs nearly half a pound more then the steel Winchester rifle.

Obviously my point is not that Stoner did not tell you that.  Just that the story he told you seems odd.

Quoted: Quoted: Not going to get a weight reduction with DI.  The weight is just in a different part.  Instead of a heavy op rod/gas piston you end up with a two piece bolt.  The added section of the bolt, the "carrier" has to be as heavy as the formally used op rod/gas piston set up.  The weight is needed in order to reliably open and close the bolt.  The weight ratio of the op rod/piston/carrier compared to the weight of the bolt is an important aspect to weapons design. This is just that internet optinion that the OP didn't want, but from an engineering perspective, DI does indeed make a weight reduction possible.  Putting the piston directly in-line with the bore allows the use of lighter parts (like using AL instead of steel for the receiver) by eliminating torquing loads and basically concentrating all of the forces involved into the bolt/BC, barrel extension and buffer tube. Maybe metallurgy has advanced to the point where the forces of an offset piston are not a problem... I guess we'll see as the current crop of piston driven AR-15s get high round counts on them.

I would go along with you here say if it worked, as in the rifle was actually lighter, not heavier.

Come to think of it, that don't make any sense at all.  Take a look at the AKM, it uses flimsy light weight sheet metal guides for the bolt/carrier, and it is under off center torque loads from a piston.

The AKM and the AR-15 are able to use light weight receivers (one sheet metal, the other aluminum)  because the bolt does not lock in the receiver, not because of thier operating systems.