TIL: the AR is not direct-impingement

[Vorpalis]

According to Eugene Stoner's original patent for what became the AR's action, it's not direct-impingement, it's a piston system. He wrote in the patent,

"...the bolt carrier act(s) as a movable cylinder and the bolt act(s) as a stationary piston..."

Further on he wrote,

"This invention is a true expanding gas system instead of the conventional impinging gas system."

When you think about how it functions, the gas isn't directly pushing on the carrier, which would be direct impingement. Instead, it's expanding inside the space between the bolt and bolt carrier, pushing them apart, which, despite functioning in a manner opposite how they usually do, is a gas piston-driven system.

Stoner's patent is #2951424, and the whole thing is viewable here:
US2951424A - Gas operated bolt and carrier system - Google Patents

I know, mind blown

Read More

 

[Misteramax]

I love this post and can't wait for intriguing minds to school me.

Let's keep the AR di for my argument with the AK. Because the AK has no true op rod or transfer piston, such as an sks or m14/garand/mini ECT then isn't the AK di too? Both have a carrier that moves only from gas influence.

 

[IronMonster]

I have been schooled on this very concept by another member here after asserting the conviction the AR was a "true" DI system...

I can't say that my feeble mind fully grasps the whos whats and hows but I accept it as fact none the less

 

[The Heretic]

DI or not (AR or AK), the AR dumps residue into the action and the AK does not. That is the issue.

DI is just one of the disadvantages of the typical AR design. The AR has a number of advantages too, especially when it comes to ergos (where the AK sucks). Everything has pros and cons.

 

[Caveman Jim]

Then the "piston kits" are not true piston action?

 

[v0lcom13sn0w]

squeeze trigger, gun fires, squeeze trigger gun fires...

thats all i care about.

nah really though, DI or not, the AR is a fine piece of engineering

 

[MrMillspecer]

This is like brain yoga in the morning. Good post. I believe the piston part it refers to is all within the BCG.

 

[The Heretic]

squeeze trigger, gun fires, squeeze trigger gun fires...

thats all i care about.

nah really though, DI or not, the AR is a fine piece of engineering

It is ok. It has good ergos and it is light and easy to field strip.

The gas system dumps crap in the action. The BGC has a lot of friction due to large bearing surfaces and an action that is not self-cleaning so combined with the gas residue and external contaminants it is more prone to problems with feeding and extraction. The gas system tube is also fragile; more than one person has found the handguard to twist and break the gas tube in the field. Magazines are fragile.

Personally, I prefer a self-defense rifle to be as robust as possible. The AK has a self-cleaning action with a heavy bolt and small bearing surfaces. The gas system is robust and durable. The recoil spring is within the BGC so it accommodates a folding stock or use in a "pistol" configuration. The materials are almost completely steel so it tends to be more robust and resistant to abuse. Mags are robust.

 

[MrMillspecer]

ARs crap AKs.

 

[IronMonster]

the old "yours is junk". "No, yours is junk" argument

 

[The Heretic]

the old "yours is junk". "No, yours is junk" argument

Both ARs and AKs have their pros and cons.

 

[Misteramax]

Mags are robust.

I feel confident in both AR and AK mags. Infact...All of my AK mags are the second gen Magpul with the stainless reinforcement. Some of my AR mags are the aluminum d&h.

I have seen my old boss do over the top destructive testing just for fun. Magpul was king. They make very ductile yet strong mags.

 

[The Heretic]

I feel confident in both AR and AK mags. Infact...All of my AK mags are the second gen Magpul with the stainless reinforcement. Some of my AR mags are the aluminum d&h.

I have seen my old boss do over the top destructive testing just for fun. Magpul was king. They make very ductile yet strong mags.

I was referring to the stock original mags, not aftermarket or other improved mags.

A magazine is the heart of the feeding system of any semi-auto firearm and its design will greatly impact how well the firearm feeds and therefore its reliability. The "lips" of the mag have a large effect on the mag reliability, especially when the mag is used/abused.

Stock AR mag:



AK47 Mag lips:



AK74 mag lips:



I can drop an AK mag on its lips all day long. I can pound on them with a hammer. They will resist deformation to a much higher degree than stock AR mags.

 

[Boboclown]

I love this post and can't wait for intriguing minds to school me.

Let's keep the AR di for my argument with the AK. Because the AK has no true op rod or transfer piston, such as an sks or m14/garand/mini ECT then isn't the AK di too? Both have a carrier that moves only from gas influence.

No. The AK is a long stroke piston. The M14 does not use the same gas system as the M1 Garand. Both the M1 Garand and AK use a long stroke piston.

The argument where an AR is more like a DI in comparison is that gas goes through the gas tube and into the gas key. The AR behaves more like a DI than a piston operated rifle. Whether its a piston or DI is somewhat irrelevant to the way it operates.

 

[MrMillspecer]

Stamped steel vs milled aluminum ,ease of mag changes, modularity, ergonomics. And most of all accuracy especially beyond 100 yards say to 500. Yes the AR is a crap where you eat design. But a good one should run 1000 rounds easy if lubed to start.

 

[Misteramax]

No. The AK is a long stroke piston. The M14 does not use the same gas system as the M1 Garand. Both the M1 Garand and AK use a long stroke piston.

The argument where an AR is more like a DI in comparison is that gas goes through the gas tube and into the gas key. The AR behaves more like a DI than a piston operated rifle. Whether its a piston or DI is somewhat irrelevant to the way it operates.

That's what I thought. The AR will always be di in my mind. The AK piston I thought well why not humor the idea. In the end the AK piston is very much car engine like. With a short burst of energy over the face of the piston, ect.

 

[The Heretic]

Stamped steel vs milled aluminum ,ease of mag changes, modularity, ergonomics. And most of all accuracy especially beyond 100 yards say to 500. Yes the AR is a crap where you eat design. But a good one should run 1000 rounds easy if lubed to start.

Stock off the shelf-mil-spec AR 15s have been shown in tests to have only slightly better precision (related but different from accuracy) than an AK-47.

Now granted - the AR design in general has a much greater potential for precision and accuracy, even with some simple tuning on up to significant modification. And sure, there are a lot of variations of ARs that are quite precise.

---

Precision - the ability of the firearm to shoot small groups at a given distance.

Accuracy - the ability of the firearm and the shooter to hit what they are aiming at.

----

Since I can (or could last time I had the chance to try) hit a man sized target at 500 meters 50% of the time when shooting offhand, I think the AK I use has adequate accuracy for me. Now granted, that was 20 years ago and my eyes are not what they used to be, but that is the human part of the equation that is failing, not the rifle.

 

[Boboclown]

That's what I thought. The AR will always be di in my mind. The AK piston I thought well why not humor the idea. In the end the AK piston is very much car engine like. With a short burst of energy over the face of the piston, ect.

Pretty much how I see it. There's a difference between something acting like a piston and it actually being a piston. At the end of the day the AR's gas system is more like DI than piston.

 

[Brutus57]

I had a girlfriend once who operated under the "delayed blowback" system.

I soon dumped her.

Brutus Out

 

[MrMillspecer]

Stock off the shelf-mil-spec AR 15s have been shown in tests to have only slightly better precision (related but different from accuracy) than an AK-47.

Now granted - the AR design in general has a much greater potential for precision and accuracy, even with some simple tuning on up to significant modification. And sure, there are a lot of variations of ARs that are quite precise.

---

Precision - the ability of the firearm to shoot small groups at a given distance.

Accuracy - the ability of the firearm and the shooter to hit what they are aiming at.

----

Since I can (or could last time I had the chance to try) hit a man sized target at 500 meters 50% of the time when shooting offhand, I think the AK I use has adequate accuracy for me. Now granted, that was 20 years ago and my eyes are not what they used to be, but that is the human part of the equation that is failing, not the rifle.

I was born in the USA as several generations before me. So I will root for the AR. Like the 1911.

Nothing against your SKS or AK , just not for me.