what?

 

No, it is not a DI gun. It uses a gas piston.

 

Piston driven

 

There are three different types of gas operated systems. The "Stoner" system is used in the AR-15/M-16 design. It is a small hole in the barrel that samples expanding gasses and routes the gas through a tube then directly applies pressure to a "cup" in the bolt. This system works well with one exception ... the hot gasses blown back into the receiver contain a lot of powder residue so after X-rounds are fired, the bolt will get sticky and malfunction. This system is also called "direct impingement".

The second system is popular in many shotguns and rifles and uses a "gas block" or "gas Ring" where a gas sample is taken from the bore and applied to linkage directly connected to the bolt. These gas block systems keep the bolt and receiver much cleaner and are more reliable than the Stoner system. Mini-14s use the gas block system. The components of a gas block system do resemble an open piston, except there is no drive rod.

The last system actually has a self contained piston and is called ... oddly enough, a "piston system". When gas from a fired round is sampled from the barrel and directed into the piston, a drive rod is thrust out of the piston, which pushes on the bolt linkage. The advantage of a true piston system is the gasses are vented up from the piston and through the handguard so none of the gasses, heat, or powder pucky is left in the receiver. Pistons are easy to adjust for optimum performance. All it takes is a "variable hole" to control how much pressure is applied to the piston. The Ruger SR 556 uses an adjustable piston system as do several other ARs. Conversion kits are available to upgrade from the Stoner system to the piston system.

 

I thought that was the difference in a short or long stroke piston? Is this just a nomenclature issue? I'm missing something here and I feel like I'm standing on it while looking all around.

 

Maximumbob54, If you look at a Mini-14 gas system, you will see a gas pipe that blows into a "cup" on the bolt linkage. This does resemble a piston, however true piston operated systems, like in the SR 556, will have an actual piston contained in a cylinder with a drive rod. Yes, there can be different stroke lengths but that's not what defines a true piston.

Think of a hydraulic piston ... hydraulic pressure is applied to a piston inside a cylinder then the piston pushes the drive rod to do the work. Gas pistons work the same only they operate very fast and vent the pressure, whereas hydraulic systems are sealed and move slower. Here's a diagram of a hydraulic piston the resembles a gas piston in a rifle. Note the "chamber" and "drive rod".

http://www.google.com/imgres?imgurl...x=114&ty=103&oei=gb9JTZ2OPIj2gAfJyaD8Dw&esq=1&page=1&ndsp=10&ved=1t:429,r:0,s:0

Here's Ruger's SR556 gas piston minus the "chamber".

http://www.ruger.com/products/sr556/features.html


Edited to add: Before Ruger introduced the SR-556, they did indeed refer to the Mini-14 gas operating system as "fixed-piston gas system" ... incorrectly I might add. They also call a revolver hand a pawl and a cylinder bolt a latch. Now that Ruger has a true piston system, they have changed their verbiage for the Mini-14 and Mini-30 to "self-cleaning moving gas cylinder", which is more of an advertising gimmick than a good definition.

 

"self-cleaning moving gas cylinder" Hahahahaha

Before Ruger introduced the SR-556, they did indeed refer to the Mini-14 gas operating system as "fixed-piston gas system" ... incorrectly I might add. They also call a revolver hand a pawl and a cylinder bolt a latch. Now that Ruger has a true piston system, they have changed their verbiage for the Mini-14 and Mini-30 to "self-cleaning moving gas cylinder", which is more of an advertising gimmick than a good definition.

"self-cleaning moving gas cylinder" I think self-cleaning is a real advertising joke. I had an early model Mini-14 Model 182 Ranch and now a 2014 Model 580 Mini-14 Ranch. I love it, BUT it is the filthiest rifle I've ever fired. The rifle, gas block and tube need an hour's worth of pitiful detailing after only a 100 rounds of quality ammo. And after only 500 rounds or so, the new 580 model was returned to Ruger for a "loose" gas tube and "violent" ejection. Ruger replaced the stock, barrel, bolt, recoil spring and repaired the slide. It is still a "violent" ejector (20-30 yards). I finally bought a Caldwell brass catcher to keep my fellow shooters on my right from injury.

 

I think my brain is being guilty of over simplifying. To me if your rifle uses gas to push the bolt back then it is Direct Impingement. If the gas hits a rod with the end result being that the rod then pushes back the bolt and little or no gas goes back then it is a piston system. Some of them have a short rod that bounces off another rod to push the bolt back. I think of those as short while models that use a full length rod that is attached to the bolt are long. I have never differentiated on what the design is that stops the flow of gas thereby using the gas to propel the bolt back. I have no doubt that you are text book correct on this one. I can however see how Ruger was using different terms until recently. Or maybe I am just being guilty of being stubborn. This isn’t the first time I have wanted to rattle sabers with the resident expert and I keep having to swallow my pride as I refuse to argue with you.