Gas assist AR vs. gas piston

[headcase]

I would like some opinions from the experts here. My area of expertise is rights. While I love firearms, my experience is with my carry pistol, my 30-30, my issued M-16A2, and a few other assorted military toys. I have been doing research on getting my first personal AR type rifle. The big question I have is with the charging system difference between the straight gas assisted models, like the weapon I carried, and the gas piston models, which I have never fired.

It seems like the main pro to piston over straight gas, would be the lack of carbon build up on the bolt carrier group. My main bitch about the gas assist AR is the amount of cleaning needed to ensure proper function. Does the piston eliminate, or greatly reduce, this? If so, what problems does the piston bring to the table? I guess what I am looking for is input from some of the more experienced members on the pros and cons between the two, as I don't know how much stock to put in the articles I have read.

If I go piston, I have been looking at the Ruger SR-556, but going through the pages here, it seems most think it is full of bugs and a Sig556 would be the better choice.

Looking for some good info so I can make an informed decision on where to start.

Thanks guys.

[Agent Smith]

This is something I'm interested in as well, and would like to know the pros and cons of the gas piston system.

[knight0334]

With a piston setup, the impingement happens at the piston which is located in the forearm instead of in the receiver like standard AR do. The hot gases and waste is vented out of the handguard thus keeping the gun from shitting in its own kitchen. ... keeping it cleaner inside.

Think of it how an AK47 works.. The gas hits a piston in the forearm, then the gases escape out little vent holes. The piston then pushes back on the bolt carrier, which then unlocks the bolt from the breech allowing it to recoil to extract and reload.

The only cons I can think of are hotter handguards after prolonged firings and reduced firing rate due to a heavier bolt assembly.

[headcase]

With a piston setup, the impingement happens at the piston which is located in the forearm instead of in the receiver like standard AR do. The hot gases and waste is vented out of the handguard thus keeping the gun from shitting in its own kitchen. ... keeping it cleaner inside.

Think of it how an AK47 works.. The gas hits a piston in the forearm, then the gases escape out little vent holes. The piston then pushes back on the bolt carrier, which then unlocks the bolt from the breech allowing it to recoil to extract and reload.

The only cons I can think of are hotter handguards after prolonged firings and reduced firing rate due to a heavier bolt assembly.

Exactly the type of response I was looking for, thank you.

Any other people with experience want to chime in?

[Lycanthrope]

The piston is more reliable...to an extent. You should be able to run a gas gun for well over 1000 rounds without issue. After that the piston gun has an advantage. The very slight downside of the piston gun is a heavier recoil assembly which will add to muzzle jump....but just a smidge.

I've also seen piston rods break so they aren't foolproof.

LycanitwasaRobinsonthrope

[Legion_Prime]

To put it simply unless you are running a can or SBR on FA stick with DI. The piston does cut down on cleaning done inside the receivers but adds a piston you have to disassemble and clean. The cleaning needed for a DI rifle really isn't that much to begin with so that's not really all THAT much of an advantage there. Punching the bore and giving the bolt and carrier a wipedown and lube after a soak in Carbon Killer should not take much more than 15-20 min. Second is the issue of carrier tilt. All short stroke pistons systems are going to have it, the difference will be how effectivly it will be dealt with. To date the only long stroke piston system I know of is from PWS, the long stroke system connects the op rod to the carrier which stabilizes it and eliminates carrier tilt. Like Lycan said there is also an increased recoil pulse from the piston, it's not a major increase but it is still there.
Knight, I believe that the slower cyclic rate from the heavier bolt assembly is actually a pro, not a con. This would be espcecially true in the shorter gas systems as it would help smooth out the shorter sharper impulse needed to cycle the action. You would also reap additional benefits in FA operation as a slower cyclic rate also means a slower buildup of heat.
Now we come to price. I haven't looked at any in the past couple months, but I'd still put money on the prices not have dropped to anywhere near being competitive with DI rifles. If you are doing FA or supressed shooting, especially through an SBR I would say you absolutely should consider one as that's where they really shine. If not then you will probably do just fine with a DI rifle (not getting into the cool guy gear factor tonight).
Alerady took my Melatonin and Nocturnabol for the night, if I think of anything else I'll be back.

[kunsunoke]

There's absolutely nothing wrong with gas-piston ARs, assuming they were designed that way from the beginning. They've been extremely reliable when fielded, even in fully-automatic mode. (LWRC has an amusing video of one of their crew emerging from a dip in the ocean, firing at will after total immersion, no jams whatsoever.) And there are a number of good choices now - LWRC, H&K, Patriot Ordinance, Stag, Sig Arms and even Bushmaster all produce piston-type AR rifles now.

DI is okay, too, having its own set of advantages (better balance; easy cleaning) though it poses its own unique set of challenges. Best choices are top-shelf rifles (by Colt, Stag, Smith & Wesson, Knight's or equivalent) with 20" barrels. DI rifles are run optimally with clean, reliable ammo and STANAG magazines. Most importantly - the BCG needs to be lubed to the point of saturation with a synthetic or fluorochemical lubricant. Petroleum-based lubricants need not apply.

[Hawk]

I'll pass on first hand info rather than what I "read on the net". I have 2 DI AR's that I have put around 5000 rounds through. I rarely clean them, most of the time I just run a boresnake through them. I occasionally oil them. I don't "run them wet". I reload for them both. I even shoot the one AR with a 22 conversion kit. The second AR I practice with weekly and shoot it in NRA HP events. I have NEVER had a failure to feed or failure to fire or failure to eject that had anything to do with the rifle or the DI system (had a mag issue once). Neither of these are Colt rifles, they both were builds. The DI system works as designed, the AR works as designed. I have zero experience with the piston system, I see no need.

[soberbyker]

What is DI?

[d90king]

I tend to agree pretty much with Primes analysis. The real benefits of the piston system are realized on SBR's with a can. That said they are much easier to clean overall. I bought a LWRCI M6A3 not long ago so I could compare it to my other DI rifles. To date I have to admit it is much easier in the cleaning department.

With a little lube I think the piston rifle can go 2500-5000 rounds with no real cleaning involved. The A3 also has an adjustable gas setting which will help it run reliably even if its dirty upfront by simply adjusting the gas setting. I also like the coated one piece BCG on the piston rifle. With its design you dont have to wory about the key, staking or the loss of gas...

As always YMMV... Best of luck whichever direction you pursue.

Here is a pic of the mid length piston and its BCG.




A better pic of the BCG