Piston vs Gas Impingement

[G8tor]

Seeing more and more about Piston ARs including Sig 516 being the lone true AR 15 platform to pass the Over The Beach torture test.

The rational behind more and more companies moving toward pistons over GI seems to be durability and ease of maintenance. Lately also reading some advantages is muzzle flash, rise and overall sound.

So two questions:

1) Is it worth the added costs for the alleged benefits?

2) Is retrofitting a cheaper way over buying a bunch of new uppers. I have a pistol length and a rifle length upper for most calibers except big bores...in some cases I have more than two uppers for more popular uppers.

My thoughts are using conversion kits as Adams Arms sells them for under $259 shipped (even lower if you want to put in the time on gunbroker.com) so in theory I could keep my current set up and simply convert to pistons on the GI uppers I think would benefit from the change.

Thoughts?

 

[Sapper771]

In my experience, no. My DI rifles are just as reliable as my piston rifle. The benefit of the piston rifle is when using a suppressor. They do run cooler and there is less fouling in the action. If that is really important to you, then get a piston.

If your set on getting a piston rifle, I would recommend going with a rifle that was designed/built as a piston rifle.

The piston rifles are heavier than a similar DI. There have also been some speculation that DI is more inherently accurate than piston. If a piece of the piston system breaks at some point, it will be a bit more difficult to fix because your local pro shop probably wont have the right assembly.....but they will probably have plenty of DI parts.

Just some things to think about.

 

[bikemutt]

Just my 2 cents, suppressed semi-autos end up with fouling, period. Piston guns collect it in one more place you have to clean.

 

[HKGuns]

If you're going to get a piston rifle buy one that was engineered to work correctly. Kits aren't worth the money.

 

[oldandslow]

G8,

All my AR's are DI and work fine. I've read that there are certain instances where a piston gun my be better than a DI gun- with a suppressor, with a short barreled rifle and where thousands of rounds are to be fired without an opportunity to clean the gun. None of that applies to me so I keep with the simpler, cheaper and lighter DI guns.

best wishes- oldandslow

 

[C-grunt]

From what I remember from several guys in the know, a piston is a good idea if you are shooting a very short SBR, suppressed, and lots of rounds.

A problem is that there is not a standard. Everyone's piston is different.

I regularly shoot my ARs for hundreds if not thousands of rounds, many of that suppressed, before I clean them. I just add oil every so often.

 

[Lafitte]

DI has stood the test of time. Well over 50 years.

Lafitte

 

[Tirod]

Seeing more and more marketing flak hyping a product line without empirical testing side by side proving the points is what is happening.

We had most of that about 4 years ago, and most of those companies went out of business. Now we have SIG and HK left. They sell their products to those who don't like or understand how DI works, or who have issues with it.

And yet DI continues it's worldwide implementation, and generally has superceded most piston guns in service where adopted. The Free world is no longer defended by the FNFAL. It's largely defended by the M16 or variants.

Like the .45 ACP, what we see are highly trained soldiers using specialty weapons because they might offer an incremental advantage they can exploit. The single stack single action handgun with external safety isn't beginner grade hardware in firearms circles anymore, especially loaded with hollowpoints. It takes some experience to keep it running, deal with it when it won't, but the results are considered - again - incrementally worth it.

Piston AR's offer that to those who run suppressors exclusively. But, aside from whether the piston is over the barrel or inside the bolt carrier, the rest of these guns are all Stoner. Controls, layout, barrel extension - Stoner thru and thru.

M16s/AR's outnumber piston guns by the millions in service, with the notable exception of the AK and it's descendants. And it's not expanding in use - the Chinese went to a bullpup, and as other countries come to the end of the AK's service life, move on to other firearms.

It can be said to still be a piston dominated market, yes, but it's not necessarily located over the barrel unless there is a specific advantage needed. And it's a very narrow application at that. There are offsetting disadvantages, and the package as a total bolis down to the AR being the better choice all around. It's just that all too many shooters are extremely conservative and simply decades behind the leading edge, refusing to adopt modern technology until it's proven beyond a shadow of a doubt that the gun isn't the problem.

Well, the gun isn't the problem, as the AR has ammo, magazines, and operator error as the top three malfunctions. And the operator chooses the first two.

No sense paying money for nothing when you and I are the main fault of the system. Practice until you can't do it wrong and any weapon will just about do. But, as consistently shown in competition and battle, the M16/AR helps you minimize your mistakes.

Choose what you like, just don't arbitrarily decide to make things harder unless you recognize why and how it will affect you.

 

[sixguns]

If you want a piston gun get one designed as a piston gun e.g. AK-47 or SIG556 not a conversion to piston like changing a AR-15. Big difference.

 

[Jackal]

They are neat, but you dont gain many tangible benefits.... I have an Adams Arms evo. While it works great, it recoils harder and weighs more than a DI gun, with zero perceivable gain in reliability. I have it because I think its cool, not because of any advantages it may have.

 

[tcoz]

Other than weight the biggest disadvantage that I see with piston guns is that they're proprietary designs so you don't have the virtually complete interchangeability of parts as you do with DI. If I ever bought one, I'd make sure it was from a manufacturer who I was reasonably certain would be around for a good long time.

 

[eldon519]

Well even with a suppressor, you can just put a switchblock on the rifle.

 

[bikemutt]

Well even with a suppressor, you can just put a switchblock on the rifle.

That's true, I like SLR adjustable blocks myself.

The bulk of the gunk which ends up in the action of a suppressed AR15 seems to get by the bolt IMO, assuming the gas block is properly adjusted of course.

 

[Tirod]

The bulk of the gunk that gets into the action of ANY self loading weapon gets by the bolt - not the gas system. It's exhausted past the case thru the chamber.

Go shoot a .22 semi auto, or your favorite self loading handgun. Wipe the casing off with a clean white rag. Residue will rub off.

Shoot a magazine thru a HK roller locked gun - no gas system at all - and stick your finger in the ejection port. Dirty dirty dirty. Gee, how did that get there? No gas system at all.

Piston fanboys ignore all that is a vain attempt to make putting the gas cylinder somewhere more difficult to clean as an advantage.

If it's a self loader, it gets gas residue in the action regardless, and it comes past the case as the bolt opens early enough in the cycle when barrel pressure is still above atmospheric. In fact, most designers prefer it as that allows the case to push against the bolt face to assist in the cycling. It also keeps the extractor from working so hard.

Get the bolt and carrier moving too soon, the case is still expanded and stuck to the chamber wall, and THAT is what rips the extractor off the brass. And why HK had to flute the chamber walls to make it let go - early extraction issues.

Anyone who thinks piston is going to keep their action clean needs to rethink it - the gas cylinder, wherever it's located, IS the action. It gets dirty regardless.

We can get to the gas rings on the AR within seconds. Literally. If anything it's almost too convenient, and the major causes of malfunction are ammo, mags, and operator error. Which is why operators who mag dump their entire basic load thru a dirty weapon causing it to jam from neglect are found next to the disassembled parts. I was never taught in training - Infantry - do disassemble my weapon down to the bolt rings to clean it in while being shot at in combat. Do it when there's no bullets flying, and do it before you eat, sleep or change your socks.

Then it works right when you need it.

There's no disadvantage to DI - why someone wants to make weapons maintenance even harder when it's a daily event is the real mystery. Go shoot your favorite self loader and see for yourself - you can trap as much gas in a remotely located gas cylinder all you want. Actions get dirty regardless. Gas cylinders are the action regardless.

 

[Quentin]

My AR won't pass the Over The Beach torture test??? Oh, darn.

 

[HKGuns]

What DI fanboys don't get is that a piston rifle is far easier to clean than DI. I own both and both have been 100% reliable.

Saying piston guns are harder to clean tells me you've never cleaned one. Cleaning the little piston is FAR easier than cleaning all the nooks and crannies in the receiver and bolt in my DI rifles. Contrary to what Tirod will tell you, the bolt and receiver in my piston rifles stay extremely clean. He is incorrectly comparing Blow back designs and mixing apples and pears.

Tirod, your information on gunk in the chamber is flat incorrect, so please just stop.

There are far more companies making piston rifles than only SIG and HK.

POF, Adams, LMT, MKE, Colt, PWS, Huldra, PWS to name a few.

The market has spoken and piston rifles are here to stay. In fact they are being called the next generation AR platform.

Let's keep the DI fan boy misinformation to a minimum please.

Again, stay far away from conversion kits.

 

[Bartholomew Roberts]

Here is an interesting link:
https://www.ar15.com/forums/t_3_118...__and_how_they_have_handled_on_our_range.html

The poster is the owner of Henderson Defense in Las Vegas. They rent out machineguns to the public and do a high volume of business. He states they have multiple AR15 variants with over 100,000 rounds on them and makes some general observations about them - including discussing piston vs. DI variants.

Spoiler warning: "- The only piston system to last on the range so far is the HK416 and TD415* system. Ever other systems we have tried has failed in one way or another. I won't say who's broke or how they broke so PLEASE don't ask. Each mfg has their own system for cleaning intervals and we may not follow their way. We have a way of cleaning and keeping records that suits our needs because of so much use. "

*The reason they are using the TD415 upper on the HK416 lower is because the HK barrel started keyholing after 10,000 rounds.

 

[Jackal]

I'm currently building a 18" upper using a Larue Stealth barrel and a NFA side charging upper/lower billet set. I'm using an Adams Arms piston kit with it. The way I figure, since its already going to be a fairly heavy 8.5lb bells & whistles rifle, I wont likely notice the extra 6oz of weight the piston kit adds. Side charging, piston driven precision AR? Why not?

 

[GRIZ22]

There are advantages to piston ARs. However, DI ARs have worked well for me for nearly 50 years. I'm not converting my DI ARs. I may buy a piston AR some day but not running out the door with cash in hand.

 

[tcoz]

Here is an interesting link:
https://www.ar15.com/forums/t_3_118...__and_how_they_have_handled_on_our_range.html

The poster is the owner of Henderson Defense in Las Vegas. They rent out machineguns to the public and do a high volume of business. He states they have multiple AR15 variants with over 100,000 rounds on them and makes some general observations about them - including discussing piston vs. DI variants.

Spoiler warning: "- The only piston system to last on the range so far is the HK416 and TD415* system. Ever other systems we have tried has failed in one way or another. I won't say who's broke or how they broke so PLEASE don't ask. Each mfg has their own system for cleaning intervals and we may not follow their way. We have a way of cleaning and keeping records that suits our needs because of so much use. "

*The reason they are using the TD415 upper on the HK416 lower is because the HK barrel started keyholing after 10,000 rounds.

That's one awesome write up with real world experience that I don't believe anybody can refute. Obviously, none of us would ever be able to run our guns that hard, but it does give an indication that there is a reliability gap between DI and piston. All other things being equal, I prefer to own the system that's held up better to the toughest possible conditions just because. That plus my aforementioned uneasiness with proprietary systems will keep me in the DI camp.
Thanks for posting the link.

 

[sixguns]

It's an excellent write up on AR's. It tells a lot of what we already knew too, and that is keep it lubed, keep it clean, replace bolts, cam pins, gas tubes, etc. often and after 100,000 rounds you should have a usable upper and lower.

 

[d2wing]

No doubt about it, DI is better. Less reciprocating mass is always better. All else being equal will be more accurate and more durable. Pistons are a gimmick that makers sell cause people buy for reasons already stated. And this is confirmed by the article other posters linked plus the experience and testing of dozens of militaries and millions of rifles in use.

 

[lysanderxiii]

We had most of that about 4 years ago, and most of those companies went out of business. Now we have SIG and HK left.....

Just Sig and HK?

ADAMS ARMS
ADCORDEFENSE
ARES DEFENSE
COLT
FD DEFENSE
FERFRANS
HK
HULDRA
LMT
LWRC
POF
RRA
RUGER
OSPREY DEFENSE
SIG
SYRAC ORDNANCE

 

[Jackal]

^^ Dont forget POF.

 

[lysanderxiii]

Well, there seems to be so many I can't remember they all.....