I've changed my mind about piston driven rifles in general, and my opinion that AR-15's should all be DI just as Eugene Stoner intended. Why the change? Got back from shooting my Tavor at the range. Cleaning a rifle that doesn't poop where it eats is so much faster and easier.

I'm considering converting my home built AR from DI to piston driven.

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-John

Meh. Gas guns wipe down pretty quick. Just like the piston/cup in a piston gun, the carrier gas chamber and bolt tail don't have to be spotless. A little time soaking in lube works if you're bent on having it white glove clean.

Either way is preference.

Simple is good.

Hmmm, I'm not convinced that it's an improvement.

Does the hand guard get hot up by the gas block? Do you end up with a lot of carbon build up there as well?

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Freedom isn't free.

Stoner's gun is ok with me.
It was designed the way for a reason.
A couple reasons, actually.

All I'm saying guys is that I used to say all the things you guys just said. I didn't think a gas piston system could be an improvement. I was a DI die-hard. There are a few guys on this board who converted their M&P 15's from DI to piston driven. I gave them the knee jerk, DI is better.

In the Tavor, it does get warm but not hot. It's a long stroke gas piston. All I have to wipe off is the piston, not the gas block. It cleans up real quick. The layout is very reminiscent of an AK and appears to be robust.

All I'm saying is that don't discount a gas piston system. During the worst part of winter when I'm stuck indoors, I'll install a short stroke gas piston conversion on my home built Franken AR-15.

DI has it's advantages. Piston has it's advantages too.

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-John

I've never discounted either one. As I see it, they are almost the same. The only real difference is where the gas pushes. One pushes at the gas block and the other pushes on the bolt.

The advantage of the piston is that the carbon is kept away from the bolt.

I can't imagine one is more reliable than the other.

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Freedom isn't free.

The one true benefit is when using the rifle in a very wet environment. We had them dunked, and they had to come up firing. Boy, did we train ourselves how to clear that chamber a little bit to ensure if it were ever needed, we would not be creating a single-shot rifle in the middle of a turdstorm.

Other than that- cleaning is a non-issue. Yeah, with use they get dirty. Spray cleaner/ spray lube will carry them for months and months. A soak in solvent will get the BCG clean when you have time to let it soak and then scrub it out. But really; they WILL run wet (Swampwater) dirty (Swampmud, sand, etc.) and they will run UGLY (Dropped, buried in junk, cracked furniture, etc.)
I like piston rigs well enough, but not enough to spend money to swap them.

One more vote against pistons. They are an answer in search of a problem. Stoner got it right.

I think some of it has to do with the ammo from the era when the rifle was designed. The AR was designed for ammo that was not corrosively primed. It doesn't matter if the primer fouling sits on the bolt for a while. (The 30 Carbine M1 also is designed to be used with non-corrosive ammo. Special tools are needed to take the piston out. The issued carbine ammo was non-corrosive even in WWII).

On the other hand, the AK, and it's parent, the SKS (which I have in addition to my Sport) were designed to be used with corrosive ammo by keeping the corrosive gasses away from the bolt.

Either system works. I suspect Stoner was trying to simplify and to take advantage of non-corrosive ammo.

I don't think DI is better, nor worse. It's just a different form of function. My AR is DI just because it is but I wouldn't have a problem with one that's a piston driven since everything else I own is piston. The only thing I would add is that be careful about the drop in pistons. A lot of them wear heavily on the receiver. If I were to buy a piston AR it would be one that was built from the ground up as a piston AR. Google carrier tilt

I doubt it has anything to do with corrosive ammo. DI has been used by other countries and long before there was non corrosive ammo.

Corrosiveness is In the primer. So once the firing pin hits the primer you get corrosive salts on the bolt and without cleaning the bolt and the receiver will start to corrode overtime. It's not uncommon to get corroded firing pins in used AKs. Neither is one a parent of the other. It's was 2 different rifles with different design ideas.

Just a quick vote for the piston.. only because the gun stays a lot cleaner. My Scar is heads and tails cleaner than my Colt Competition was..

Pick up any gun magazine and you will see ads from major manufacturers that now have a piston version in their inventory. The arguments against a piston gun are usually made by people who have never even shot one, much less cleaned one. The added weight comments make me chuckle because the weight of my piston assembly weighs a whole whopping 6 Ounces...much less than added lights, lasers, or Bi-pods that clutter today's rifles. I can thoroughly clean my M&P 15PS in less than 15 minutes. My gun is now 3 1/2 years old and never malfunctioned in any way. As long as they both go Bang, who cares?

Same arguments were made years ago when the first automatic transmissions first came out....people said they were junk and would never last.

Good news! AR-15s are piston systems without the operating rod! Everyone wins!


Ok, I'm done.

I'm a long stroke piston fan. PWS makes an excellent product. I like being able to adjust the gas quickly for going between suppressed and unsuppressed. Yes DI rifles can have an adjustable gas block I'm aware of that. They do run cleaner too. I can run 500 rounds suppressed through my piston sbr without cleaning and zero malfunctions. For those that don't shoot suppressed it will get dirty much quicker. It is nice to take a carbine class and watch others cleaning their rifles before the day is over. I don't mind cleaning, but I'd rather spend my time putting rounds downrange.

I just know I didn't care until I bought a piston upper just because it was a crazy sale. Now I hardly ever shoot the DI one. I did just buy a 6.8 upper and plan on dropping in a piston package into that one as well.

Do you change out your suppressor a lot? I know I don't. Then again, if I'm too cheap to buy a piston conversion, I'm way to cheap to jump through the government's "Mother May I" program to get a suppressor.

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Freedom isn't free.

And, given our location (PRK)....... the only way I make my rifle quieter is by shooting it in an outhouse.

I like piston ARs when a suppressor is used. Especially in select fire. (First experienced the difference when invited to a shoot with a couple of H&K reps returning from a demo at Ft. Benning. We brought "old school" and they brought their newest!) Otherwise, have not felt the need.

BTW, Stoner wasn't against the piston design. Prime example? The "low tech" (i.e. easier to manufacture) AR18/180. That design never really left the starting gate due to lack of sales. Only real weak point in that 1960's design was the stock's hinge and lock, so....

Not a lot, but I have only one 30 cal can and more hosts than I care to mention. Each has a fast attach muzzle device, so really I just move the can from host to host depending on what I'm wanting to shoot and the rifle may have been previously setup for non suppressed so I need to change the gas.

Exacty this....
E. Stoners attempt to improve & simplify the shortcomings of the AR15 design with his gas piston AR18/AR180 design which followed shortly after .

Granted the weak link of the AR18 was its lightweight plastic folding stock then again it did not see the battle field developments the AR15/M16 did either .

Also while not publicly discussed its fairly apparent the bolt and guide rods are almost identical to the British L85 Light Infantry Weapon after viewing their parts breakdown, (they eliminated the flimsy buttstock by incorporating it into the buttstock).
Probably no coincidence that Sterling of England was making the Ar180 under license at that point.

L85 breakdown


AR18/AR180 breakdown (Compare the dual guide rod, receiver hole pattern and spring loaded action cover)
Note that the bolt is a top view in this pic...


Comparing the L85 bolt group in top pic to the AR18/AR180 bolt pictured below and oriented the same way reveals they are almost identical.

Actually, Stoner's original design for a "low-tech" version was the AR-12, which still used the DI he favored. After Armalite's parent company, Fairchild, sold the production rights of the DI system to Colt (along with the AR15), the design legally had to change to a short-recoil gas piston of the AR16, which later became AR-18. Stoner left Armalite in 1961 and AFAIK was not involved in the conversion to gas piston.

I don't know what Stoner really thought of gas piston. Just want to make sure credit is not given where credit is not necessarily due.

Curious....does parts availability for the future factor in this?

Yes. The service life of an AR-15 barrel is anywhere between 6,000 to 10,000 rounds. I figure that at that point, I'd have to replace everything else too.

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-John

If the shooter does not run the barrel WFO and do many mag dumps, the AR15 barrel should last WITH accuracy for at least 10,000- 15,000 rounds.
Making the barrel glow will shorten its' life considerably......

Granted, I am talking about the kind of accuracy that a standard rifle gives up; not a Les Baer hot-rod.
I've got 2 with over 12K on them, and they both shoot well without keyholing. And, they have been eating that evil Russian ammo the whole time.

As engeneering concepts DI and various piston designs all workn and generally work well.

But when I want a piston gun on purpose , I'll get one that was designed that way on purpose instead of a DI based platform reimagined into a piston.

YUP!!

Shot from my M&P15 PS (Piston) at 100 yards, bench rest, EOTech XPS-2. Best rifle I have even owned. The 3 shots outside of the red circle were shot with my Magpul BUIS.

Indeed.

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-John

The Piston works fairly well in the AK47 and SKS...
My favorite piston driven rifle is this SLR;

It certainly does for me which is why I stick with DI ARs.

Just so I can understand this stuff-my Mini 14 would be considered piston driven, correct??

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Forum consigliere

Ruger Mini-14 is gas operated, semi-automatic only weapon which uses Garand-typerotary bolt with two lugs. Action is operated by the long-stroke gas piston,which is located below the barrel and is concealed within forend of the stock.The gas piston has cup-shaped head, and is linked to the bolt via Garand-typeoperating rod which runs at the right side of the weapon. Manual safety also patterned after M1 Garand or M14 rifle, and is located at the front of the triggerguard.

As per this article I found.
Modern Firearms - Ruger AC-556 Mini-14GB

Just like the eternal Chevrolet v Ford debate, neither side in this argument is likely to convince the other they are wrong or give sufficient reason to switch. Neither side is as wrong as the other wishes to convince them they are.

Come on... nobody in their right mind would buy a piece of chevy!!

Well yeah... but since when did that matter? The same can be said for most every accessory/mod ever made for an AR.

they make accessories for AR's??

I won't own a ford. I have made too much money dragging them off the highway and fixing them to ever trust one.

I've never had a piece of chevy outlast the payments.. GM is not in my future!! YMMV

Yeah, you may have a point. Even so, the EOTech I've added is a vast improvement over the iron sights. The free float forearm made the gun measurably more accurate. The muzzle brake reduced the muzzle rise a quantifiable amount.

So, many things I've added were things that made not just noticeable improvements, but improvements I can prove. The piston system is different for sure and certainly not worse than the original system. But, is it as much of an improvement as some other things I've added? Maybe, but like I said, I'm not convinced enough to plunk down the $$$ to make the upgrade.

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Freedom isn't free.

Well, I really haven't added to my Sport. I, however, have replaced two parts on my Sport, an LMT adjustable rear for the MBUS, and M4 handguards with heat shields for the stock handguards. But, it sounds like many people replace those parts anyway so maybe S&W installed the bare minimum because most were stripped off quickly after purchase.

As for the piston system, I understand the benefits but I will probably not install one. My goal is to keep my Sport as light, simple, and inexpensive as possible.

You could go import then.

I've had 3 Dodge trucks in a row now with no problems...

My '07 Tundra is truly American made by Americans in San Antonio, Texas. Best truck I have ever owned and after 109,000 miles the only thing I needed fixed at the dealer was the Made in China radio. I have owned all of the others at one time or another, and all had major problems after a few years. I'd buy another Tundra in a heartbeat.

My M&P15 Piston has given me the same reliability as my truck, and I will never own another DI gun again.

With all due respect...the FACT that the DI version of the M-16 is still around and in ACTIVE service some 50 years AFTER introduction speaks VOLUMES for the "platform."
I personally CARRIED an M-16 into combat in 1978 and it NEVER...NOT ONCE, NOT EVER, NEVER, NEVER, NEVER, failed to chamer, fire, extract, eject, and RE-chamber for me!

I carried that ******* up and down the mountainous rain forests of Panama and it NEVER failed...NEVER! I'm not quite sure exactly what a "gas piston" system can bring to the table to make me think IT is the proverbial "Cat's Meow!"

Today I own a "rack" of AR type rifles, all DI, and ALL have worked 100%

Just saying...for the sake of those who buy the AR-15, "as is" and don't necessarily want to drop $300+ into a piston conversion!

For all those who have shelled out CASH for a "Mil-Spec" operation AR-15....YOU'RE perfectly FINE with the DI system!!!!

My 92 3500 had 350K on the odo when the 2011 wildfire got it. I've owned a few Dodges. Even and AMC or two. The closest to a Ford has been a Mazda. I'm not a brand groupie. I buy what interest me.

Oh to get back to the subject of the thread. Piston ARs do not.

JaPes, I know this is an old thread but what is your opinion of the Piston Driven rifle compared to the DI rifle.

Any new updates?

Nothing new.

I prefer civilian semi-auto rifles patterned to look like military only rifles that have gas piston systems native to their design. The reason I prefer gas piston systems has not changed: they don't poop where they eat and I find them easier to clean. There is nothing blowing back into the action, the receiver stays clean. Combustion gas carbon fouling is concentrated at piston. Of the two types of gas piston systems, I prefer the simplicity of the long stroke gas piston system (piston, connecting rod, carrier all one unit) to the short stroke gas piston system (piston, connecting rod, carrier separate pieces).

I will say that there is nothing wrong with the DI AR-15. There is no added reciprocating mass of a long stroke gas piston. There is no added complexity and small parts of a short stroke gas piston system. The DI system is stupid simple. Replacement gas tubes are cheap. Replacing gas tubes is easy.

While a piston AR-15 doesn't poop where it eats, there are negatives. The AR-15 is built on standardized parts and dimensions. A gas piston is not native to the AR-15, so gas piston systems are not standard across all AR-15's. Choosing to buy a piston driven AR-15 locks you into a single source of gas system parts and matching carrier key. Building your own gas piston AR-15 or converting an existing one adds to parts selection deliberation and complexity because the system is not native to the AR-15. Which piston system to use? What carrier to use? How does the system cope with carrier tilt? Do I have to purchase a special buffer? IMO, if you want to go the gas piston route on an AR-15, buy a factory complete gas piston AR-15.

Regarding converting my AR-15 to a short stroke gas piston system, I didn't do it. I abandoned the AR-15 platform. A Tavor and AK-M cured me of black rifle disease.

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-John

Until the Tavor is as cheap as a used 6920 I'm sticking with the AR.

Dispite having mostly long stroke gas pistons I actually prefer the short stroke. Don't know why, not for any real reasons. The two are practically the same thing.

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Ill take my Scars any day !!