AR-15 questions on Piston models

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TexasEd

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In looking at the gas impingment models Colt, RRA, Daniels Def. etc. they are the old stand-by. However I have spoken to some that swear by the newer gas piston models (HK, LWRC, etc). I know they are more money but it seems that they are less to take care of and the life of the rifle is projected to be longer. Any thoughts would be great.
 
Hi
I have used the adams arms kit on my m-4. I have nothing but good things to say about it. So far it feeds everything from wolf to winchester. No problems with system. I went for the new one piece carrier. I had a few failure to feeds but it was a pmag. toss that and works as an ak does. I got mine from srt supply thinking of doing my 6.8 this way also. It's an optional mod but most of new specs on us rifle are a piston system . only haven't decided on caliber. It's a cheaper alternative to a scar /acr or fn. I had to ider a rail to match clearance of piston. but i already had mine free floated so just a swap out and good to go. If you use a arms rail or have a spacer may have to adjust to keep cowitness.
good luck
 
I love mine, it's an Addax/PWS system. I can't get out to shoot her, do to incliment weather, but I look forward to shooting the 600 of PRVI ammo I have set aside just for break in.

512 EOtech
Troy rear Battle Sight
Troy front battle sight HK style.
Magpul MIAD
Magpul MOE
Spike's Tactical Lower
DPMS LPK

Addax Tactical GPU
* 1:9 Sabre Defense Chrome lined mid-length
* M4 Feedramps
* Daniel Defense 12.0 Light rail
* Addax/PWS Bulldog FCS


GPU4.gif

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I have a POF (IMO superior to both of the brands you mentioned), and it is great. A breeze to clean, and is still WAY more accurate than i am. The main advantage of a piston system over a WELL BUILD DI gun is the ease to clean.
 
Gas piston operation keeps the the gas system & the bolt cleaner and cooler. Clean and cool will equate to longer life and better reliability. It is really that simple.

As far as CMjohnson's third hand comments are concerned he mentions absolutely nothing about design changes to keep the bolt in place on gas piston AR's. His argument against them is completely invalid. If the gas pressure were key to keeping the bolt in battery don't you think a company like HK would make compensating engineering changes? Like they're really going to build a rifle that won't stay in battery!

His assumptions and third hand information are all generalizations.

There is more proof available as far as the hot/cold issue is concerned. The video below mentions it briefly.

http://www.discoverychannel.co.uk/video/elite-forces-hk416/
 
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So tell me HK, what exactly is your wide reaching experience with firearms. Because the tests from the Feds and the Military say that is EXACTLY what HK built.

I only ask because in this thread and others your comments are more of that of a fanboy than someone who has actually handled, or read the test reports from groups that have done extensive testing on these weapons.
 
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Dear Tex, I have had the LWRC now for about 6 months and ran about 800 rounds through it without any issues whats so ever. The Piston system has really be great operational wise, and with the suppressor on is the only way to go, as far as heat and fouling build up.* I would not hesitate to recommend* one. Now thats not to say the old gassers are going to be replaced, because the cost of the LWRC was twice the price of an gas op upper.
 
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Save your money and clean your rifle after every range session. I have never had a failure due to the lack of a gas piston system. The current gas blowback is reliable as long as you clean and lube your rifle.
 
I am leery of generalizing from one anecdote to general principles, but I ran across the following report from a very, very muddy carbine class recently. As with all anecdotal reports, take it with a grain of salt, since the superior performance of the LMT piston AR vs. the DI AR's could just be because the other AR's weren't LMT's. Note also that the DI AR's worked if guns and mags were kept scrupulously clean.

http://www.warriortalk.com/showthread.php?t=54199

Reliability during 2 days of mud

I wasn't going to do a post on my experience this weekend because the topic has been addressed to a certain degree before, and because the experience arose from the Fighting Rifle class with Tactical Response in Camden, TN, but Randy made me do it, so here goes.

I took the fighting rifle class with TR (Yeager's group) to see what they were all about. The class was good quality. It is interesting to see how the concepts are taught by different groups. We started with handgun and transitions with a curious wink and nod by the instructors. Nuff on that.

Getting ready and on the drive over, I knew it had been raining for a week here in TN, and was going to continue to rain all weekend, and I was having second thoughts about going at all. I knew it was going to be disgusting mud and wet and discomfort, but, my mother in law was in town, so on balance...(no kidding)

I took my AK as I had the most practice ammo set aside for it. The class was composed of 22 people. About 2/3 running ARs, 1/3 AKs.

Following initial warm up drills in the morning the first day, the afternoon was moving and shooting from all positions, team and solo, and everyone was on the ground, up, down, with many mags not retained under stress, and mud everywhere. During the afternoon, the ARs began to fail sporadically and continued through the end of the day.

The next day was intense team drills, bounding in all directions, with round counts running up to 180 or so. The ARs failed all day. By the afternoon teams of people running ARs would both have FTFs after a few shots, and have to transition to handgun, then they would run out of ammo. Total round count day 2 was about 1000 to 1200 rounds.

The AR failures were really disturbing (particularly to the AR people). Everyone knew that had this little escapade been real world, a lot of people would have died, missions failed, end of story.

Apparent reasons for AR failure: Mud and dirt in mags, mud and dirt in gun, rain then sun then rain then sun seemed to make the usual carbon issues worse. Forward assist was required all the time, and running ARs ejected only a few feet. 1 AR that continued to work was thoroughly submerged and washed off (with mags) in a stream between each drill. The operator of another refused to allow any mag to touch the ground (he had a department issued gun that was not allowed to get dirty or scratched). There was one Robinson Arms XCR which ran just fine both days on Wolf, until the trigger spring broke. There was one Lewis Machine push rod AR that had only one FTF which appeared to be ammo related (which was a real testament to Lewis Machine). None of the AKs had any failures. And none of the AK people cleaned anything - mud on mag, wipe off the big stuff with wet muddy glove, click, rack, bang bang bang bang. It was really quite amazing.

Lessons learned: Going into the field for a couple of days is different. It is so totally necessary to train under the bad weather conditions to see what works and doesn't because what can fail will fail. If you learn to operate in bad conditions, you have a HUGE advantage. Field load of ammo needs to be as much over 180 as can be carried without significant inhibition of movement. One 7 minute altercation with flanking attack or retreat under fire will take all 180 rounds. And last but not least, the AR has serious limitations in harsh environments; the operator really needs to work it out in advance (which is possible) or change to something more forgiving for field work. If it can rain, if it can be muddy, if I can fall in a ditch or cess pool on a sunny day, it will happen. The AK was not only forgiving, they were total pigs - if they could have smiled ugly, sharp edged grins while wallowing in their own filth, they would have. Reminds me of what a friend of mine used to say, back in the olden days: "Dude, she may not be much to look at, but she's got enthusiasm, and enthusiasm goes a long way."

Hope this info finds you well.

-Aaron in TN
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My bet is that you will not see a statistical difference in overall performance from top shelf DI vs. GP AR type rifles. (acronym Dr.W used GPAR) You are going to get equal arguments from both sides, so in the end know that if you buy a top shelf gun you will get top shelf performance.
 
We all intuitively know that the gas piston is the way to go. Don't fight it...
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Oh brother :p ..... I am suspicious of the non-scientific, anecdotal nature of the warriortalk report; possibly the veracity as well.

I belive gvnwst when he says that their main advantage is ease of cleaning. Might they be more reliable in the field under muddy conditions? I don't think we've yet seen a non-biased valid scientifically-controlled study to prove this, have we? They *MAY* be more reliable with mud in the guts & mags than a DI AR15, but I'm skeptical that a short stroke piston is more reliable than a "short stroke impingement".

Now a LONG-stroke, like a Robinson XCR or AK47 type, OTOH.....
 
The problem with direct impingement is purely political.

Robert McNamara sent out boys in VietNam M16 rifles WITHOUT cleaning kits clamming they were "self cleaning".

THAT is what caused most of the reliability problems with the early M16s, and those problems have haunted the AR platform ever since.

The reality is the DI system works just fine, I've put thousands of rounds through several ARs and never had any problems with them. Every AR I've owned has a forward assist ... can't say I've ever actually used it.


Gas piston uppers are nifty ... I imagine the only way you're really going to notice a difference is if you're running a suppressor.

For the most part, however, I don't think they're worth the extra cost.
 
We're not likely to ever see a non-biased,scientific test. TOO MUCH MONEY IS AT STAKE. If one were to start with a clean CAD screen it's not likely that a DI system would make it into the Design Specs. That's all I'm sayin'.
 
If one were to start with a clean CAD screen it's not likely that a DI system would make it into the Design Specs.
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If cost wasn't a factor you'd probably be right, but when outfitting an Army, cost is ALWAYS a factor.

A DI rifle is cheaper to build and it works well enough.
 
Now a LONG-stroke, like a Robinson XCR or AK47 type, OTOH.....
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Well now...TECHNICALLY speaking...the AK is not long stroke.:p I can't remember the technical definition, but when you find it, a lot of "long strokes" are short stroke, and vise versa. If a AK is long stroke, by design, so would a POF be, but POF says it is short stroke... Really, i am not convinced that there is a big difference from long to short.
 
I hate to be nit picky but hasn't Ruger made a pretty bonehead move by saying this is better than "gas driven rifles".

What makes the piston move if not gas? :)

Maybe they should have worded that better.......
 
If cost wasn't a factor you'd probably be right, but when outfitting an Army, cost is ALWAYS a factor.

A DI rifle is cheaper to build and it works well enough.
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Yes, cost is such a factor... Not, really. We were the wealthiest nation in the world at the time. COST wasn't the driver, but WEIGHT probably was.

And just how "well enough" would translate to, say, the Eastern Front during winter? There is enough "controversy" for the conditions in Iraq as well.

Notice how no other modern carbine or rifle is Direct Impingement. Hey, I'm just an engineer's engineer and DI would NOT be a consideration if I were tasked with creating a battle rifle or carbine and you'd have a helluva time trying to convince me of the merits of DI on a "clean sheet of paper" design.
 
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