Gas Piston Uppers for the AR

[William_Munny]

Anyone have lot of experience with GP AR uppers? I was eyeballing a CMMG 6.8 upper but would like some input on the characteristics (reliability, accuracy, etc.) of the product. Also is it true that the GP upper negates the buffer and springs so that a folding stock can be attached?

Thanks!

[Smith]

Most GP guns still utilize the buffer and springs. The best out there are LWRC and POF IMO. All the other manufactores are using Ares, Adams, or Osprey kits you can get aftermarket. The main thing is how the GP interfaces with the bolt carrier. The better ones take care of the tilt you get with GP, while the others just accept it and wear in places you don't want like the buffer tube threads ect.

[Guest 6.8 AR]

I don't have one, but I have been eyeballing them for a couple years. That said, an AR with a

piston won't give you more accuracy, but maybe help with reliability, due to the bolt carrier

staying cleaner and cooler. That would probably help in auto, but not much in semi auto, unless

you rarely clean your weapon.

That's the main reason I haven't bought one of the piston kits. I don't see the benefit.

The gas piston only pushes the bolt carrier back, but still needs something to close it. That's the

buffer and spring and there may be some stocks that have a different spring configurations.

You're really starting to talk about a different weapon, other than an AR 15.

[William_Munny]

Thanks !

[bigwakes]

My most recent AR is a mid length gas system, because it is suppose to have less stress on components. I have heard gas pistons have an even bigger impact on stress to components and are cleaner. The only reason I have not considered them yet is comparability. It seems like everyone is using their own system and parts. I wish someone would come out with one system adopted by all major manufacturers.

[Guest coburn]

I have a POF 18" upper and love it! They are smooth shooting, incredibly reliable, and with the bolt assembly and upper receiver being nickel teflon plated, it is super easy to clean.

[Guest DanE479]

I do not buy the reliability argument.

A DI system puts carbon and gasses into the chamber. At least you can clean that. Why is it automatically assumed that the same gasses and debris will not foul the port and mechansim attached to the barrel that activate the piston? It's a lot harder to get to those components to clean them, isn't it?

Meh, get a mid-length DI system and you will have about the same recoil as a top end Gas system, and total parts compatibility with all other DI ar's.

[Dolomite_supafly]

For me I would like to try a piston setup but as far as reliability goes I do not see them being any better than the proven DI system. I understand why they should be better but have yet to really seen documentation of a real world difference between the two. A quality DI rifle is going to be as reliable as a quality piston rifle.

There have been a lot of documented DI AR's going thousands upon thousands of rounds without cleaning. I have persoanlly fired over 3000 rounds on a trip without cleaning. On number of my trips overseas I would practice weekly, firing 300-500 rounds every week for 8-10 weeks. Definitely over 3000 rounds. I would break the gun down at the begining of my trip to make sure no parts were broken and to give the weapon a good cleaning. The next time I would break it down would be at the end of the trip to clean it before turn in. Yes it was very, very dirty but it never had any type of malfunction.

I will try to find my post detailing all of them but one in particular had 4800 rounds of Wolf, yes Wolf, without cleaning. It is in the archives of AR15.com but you can't see it unless you are a paid member.

Here are a few others:

15K rounds of Wolf without cleaning

Pat Rogers school has a rifle that is rented that has documented more than most:

BCM Complete AR15 Upper and Lower Receivers [2010-01-01] - 03DESIGNGROUP

Here is the most recent article about "Filthy 14". Yes they did finally clean it after firing 26,245 rounds without cleaning.

http://www.bravocompanymfg.com/v/vspfiles/assets/images/filthy14_oct10.pdf

So for me it is more snake oil than actually needed because when was the last time any of us fired 25K rounds without cleaning. I'll admit I am not a big fan of cleaning my AR but I have never made it to 25K rounds using a single AR, without or without cleaning.

Rather than spend the money on a piston setup I would buy more ammo and practice. I would also buy some of the normal wear parts of an AR. Buy a few disconnects, a few extractor springs, a few hammer springs, a few trigger springs, an extra firing pin, extra gas rings and maybe an extra bolt hold open or two as well as a extra set of hammer/trigger pins. These are the parts I see fail the most with the extractor spring and disconnect being the top two.

Dolomite

[William_Munny]

Awesome input Dolomite!

[LA_357SIG]

An Osprey-416 piston retrofit I installed on my x39 build. Still need the recoil spring and receiver extension.

I have no doubt the DI system works and is far better than a piston system for an AR-15. I also believe the piston system is the best system for other platforms. Just not for the AR-15 system. It creates more problems than it solves. BUT since I am a tinkerer and like to try different things, I will try this piston system on my carbine length 7.62x39mm AR build. God Bless America...

[PC7]

The piston is more reliably because you don’t have those hot gases blowing back in the receiver, gumming and drying the action. The difference is that in the piston system, the excess gases and carbon are vented at the piston into the air and not into the action as in the DI. One can see the result of that in the above pictures.

If the piston AR is all hype, then why did Tier 1 US Special Operations have the AR piston created and still use it with great success? Further, the US Army is in the process of purchasing piston uppers for the current M4’s and are also having a forthcoming piston carbine comparison. Do most civilian shooters need the reliability and robustness of the piston AR? No, but they are sure easier to clean.

[Guest DanE479]

To PC7:

Please quote your sources for the following claims:

THat the Tier 1 teams had the piston AR created (THe Piston AR system has been around for a while. LIke 1970's for a while)

THat the US Army is purchasing piston uppers and fielding them in combat with no discernable logistics train

That the Piston AR is so much more reliable. (GO check out the article on Pat Rodgers's "FIlthy 14" carbine).

What makes you think that all of that crap that is normally blown into the chamber in a DI system won't foul the port that actuates the piston on a gas piston system AR? It's a lot easier to clean the chamber in the upper than it is to clean the actuator port...

Also, how do you address the problems of bolt carrier tilt in the Piston AR's given that the BCG is not riding on steel rails in the upper?

It's one thing to be able to read the internet and regurgitate it. It's another thing entierly to understand the fundamentals of a weapons system and how it works.

[PC7]

To PC7:

Please quote your sources for the following claims:

THat the Tier 1 teams had the piston AR created (THe Piston AR system has been around for a while. LIke 1970's for a while)

THat the US Army is purchasing piston uppers and fielding them in combat with no discernable logistics train

That the Piston AR is so much more reliable. (GO check out the article on Pat Rodgers's "FIlthy 14" carbine).http://www.tngunowners.com/forums/newreply.php?do=postreply&t=52766

The USA’s M4 Carbine Controversy

Army announces carbine competition details - Army News | News from Afghanistan & Iraq - Army Times

This article/s should answer all your questions; if you doubt the validity of it, just check the sources/references listed at the end.

I did misspeak on the creation of the piston AR, it was created decades ago. My intent was to communicate that HK created/perfected the modern piston AR for the US Army, and thus started the current piston revolution.

Also, how do you address the problems of bolt carrier tilt in the Piston AR's given that the BCG is not riding on steel rails in the upper

Carrier tilt is not an issue, due to their manufacturers design, with LWRC and HK piston AR’s. I can’t speak for the others however.

What makes you think that all of that crap that is normally blown into the chamber in a DI system won't foul the port that actuates the piston on a gas piston system AR? It's a lot easier to clean the chamber in the upper than it is to clean the actuator port.

Are you serious? Reread my first post. If you still don’t understand, it leaves one to assume that you have not used and/or cleaned both systems.

It's one thing to be able to read the internet and regurgitate it. It's another thing entierly to understand the fundamentals of a weapons system and how it works.

Don’t be so hard on yourself.

Edited February 20, 2011 by PC7

[Vindice]

I was in a gun shop yesterday listening in on a conversation about this between two of our boys just back from the sandbox over seas. I've been interested in building a piston system now for about a year but they had quite a bit to say about it. They were saying that several units had them over there but they were having a problem with severe failures after about 10k rounds. They said that most of the units were requesting a switch back.

That said I'd still love to experiment with one... I enjoy it on my AK but don't know if I'd take one into combat after what they were saying.

[50 cal]

If you were to truly understand the mechanics of the DI system, the gas fills the gas chamber of the carrier and slightly pushes the bolt forward in the carrier as the carrier fills with gas, as it fills with gas then the carrier slides to the rear. This alleviates the pressure against the bolt lugs

A piston system just rips the bolt carrier back away from the breech. That is the cause of some broken bolt lugs.

I tried a piston system. Went back to DI. Like it much better. The gas build up on the bolt is self limiting. It will build up so far, then stop. I just lube the crap out of my rifles, shoot the piss out of them and most of the carbon wipes out with an oily rag.

Piston systems are a solution in search of a problem. Sure, they work for the AK style rifles, but their locking lug set up is entirely different.

All this "Tier1" operators using piston systems is crap. They may have experimented with them at Battle Lab at Ft. Benning and saw very limited use in the field, but widespread use? I seriously doubt it.

[Smith]

Lot of top notch info in this thread!

Bottom line is this , the legitimate complaints of the GP are weight and balance. Pro's are much cleaner and cooler.

All the rest is hearsay, preference, and BS. The military will eventually use a GP system like everyone else, so pick whatever you like. Just don't feel the need to have the military's preference justify your choice.

[William_Munny]

Lot of top notch info in this thread!

Bottom line is this , the legitimate complaints of the GP are weight and balance. Pro's are much cleaner and cooler.

All the rest is hearsay, preference, and BS. The military will eventually use a GP system like everyone else, so pick whatever you like. Just don't feel the need to have the military's preference justify your choice.

I already did, I got a 16" CMMG 6.8 SPC GP Upper... I am painting the chassis and furniture coyote brown and hoping to shoot in two weeks...

[LngRngShtr]

LR 300 Kits

for an AR that doesn't use the buffer and springs,.. called a DGIS or delayed gas impingement system ..Para Ordnance Ltd. now has the design in their Para Tactical Target Rifle

I used to live in Mass. and Al Zitta would bring one of these to USPSA matches back in the mid/late 90's kind of odd to not hear a buffer spring..and suppressed,..now that's just a ride..

John

[crashgordan]

interesting thread...

i've got both...

have years of time on DI systems, and like many have said they can run filthy. i have a test mule with +10K rounds, never cleaned, never malfx. Nasty dirty.

I recently began running a Adams midlength system. The jury is still out as i've not gotten near the 10K mark yet, but i can tell you, there is no comparison when it comes to cleaning. none. I can run the gun hard and pull the BCG out of it and hold it in my hand. and although i'm 6K into this one, it's still basically clean and showing no signs of lug wear or carrier tilt.

the problem, as i see it is not so much the gun ***ting where it eats, carbon and hot gas has to go somewhere, and it does in both. However, in the DI, it's dumped into an area that, by all accounts, needs lube. mix the carbon and lube and get 'mud'. Cook off the lube after 500 or so round (unless you are smart enough to use SLIP2000 - there is nothing better) and the mud gets hard.

The carbon and hot gas in the pison are all out front, out of the action and mixing with very little lube, and s***ting in very few moving part. the piston moves very little, unlike the DI bolt/gas key/rings/extractor/ejector/locking lugs/ and all the moving parts that keep the DI system running.

I love me both.

Certainly, running a piston mule has not caused me to sell all my DI systems, won't happen.

and yes, the Piston is driving the bolt and lugs very differently, and not the way they were designed, and this is the only downside i can find.

There's a reason systems like the the FAL and AK run forever... loose tolerance and keeping the heat and carbon out of the action.

just my thoughts...

[LA_357SIG]

Though I'm not totally sold on piston AR's yet:

1.) Runs Wolf 7.62x39mm hollowpoints

2.) No carrier tilt

Osprey Defense OPS-416 retrofit kit