Wednesday, September 08, 2010

Oh, look...

...another gas-piston AR upper. How innovative.

I'll give this RRA unit some props, though, in that it uses a proprietary bolt carrier, like the ZM Weapons Yankee Hill Para TTR.

Look, if you've just gotta have a gun with a piston in it so your friends will know you're cool, get a gun designed from the ground up to use a piston, not some kludge affixed to a Stoner-type bolt carrier assembly that was never intended to have a foot-long lever torquing it from the top.


Unknown said...

I agree. They don't do anything for me. I clean my AR after every match or practice anyway.

The Raving Prophet said...

Right now I don't see the point for one for me. If somebody wants one, so be it. However, if they redesign the system to the point where there's no longer a receiver extension/buffer tube and the gas system is completely different, is it still considered an AR-15, or is it a new design derived from the AR platform?

On the upper, while they might be able to use the same bolts and barrels as a regular AR, I'd expect everything else would have to be quite different. The lower would be the same (except for the obvious lack of a buffer spring, buffer, and retainer), but not the top end.

Why should the 1911 folks have all the fun of declaring what is and is not the "pure" and allowed form? Now black rifle fans can get into wars over heresy too.

Tam said...

I'm not talking about the "purity" of the AR. What I'm talking about is the dumb idea of hanging a long piston off the upper forward edge of the AR bolt carrier and then wondering why it or the bolt or the upper receiver cracks a few thousand rounds later *coughHK416coughLWRCcough*.

NotClauswitz said...

I have two piston guns already, an M1 Garand and an M1 Carbine. :-) One shoots a bigass-round and the other shoots a pistol round that's nearly Europellet worthy. No wonder the Bavarians liked the Carbine.

Außenseiter said...

What's the whole point of AR's anyway? I just can't get excited about them. My mind just thinks "meh". Same for AK's. Ugly as sin.

Now, an M-14 or Garand with a real mag, there is a neat rifle I'd like to own. Maybe I should get one of these surplus WWII Soviet semi-autos.

McVee said...

I've recently desired an AR having never owned one. I have read all the reasons why I should avoid the AR/DI platform like the plague. The more I've researched tho, it seems to Me that the contemporary lineage of AR's suffers from a hasty generalization of past and present anecdotal evidence. Modern DI AR's just work and reliably so. Heck of alot more affordable too!

Tam said...


"What's the whole point of AR's anyway? I just can't get excited about them. My mind just thinks "meh". Same for AK's. Ugly as sin. "

To shoot.

Stuart the Viking said...

A piston on an AR is a solution looking for a problem. Yes, the bolt gets hot (big deal), and there is some carbon, but a shot of oil in the key-way on the bolt every so often and for what most of us will be doing with an AR it will run a rediculous number of rounds before it starts to have trouble. I can imagine that by then the piston AR will be having issues with carbon buildup in the piston and will likewise be having issues. For me, I KNOW how to dis/re-assemble the basic system blindfolded, with a piston AR, not so much.

Oh, and a piston AR has more parts, therefore more chances for a part to fail.


Anonymous said...

"What's the whole point of AR's anyway?"

Mine is a very effective SD tool that can be used by the whole family, many of whom can't use something like a shotgun nor a pistol caliber carbine (the blowback mechanism makes those bolts hard to operate on many of them). Very low recoil, easy to use controls, and a 30 round mag.

The AR is a reliable, simple, durable weapon that is easily maintained. It has a superb system for optics mounting. Parts, magazines, and accessories, as well as ammo, are all widely available.

It's comparitavly affordable, in that it costs more than some AKs but less than M1As and rifles like the AUG, FN2000, ACR, etc.

I view the AR as a modern day M1 carbine that shoots better rounds. Light, easy to use, simple.

"I've recently desired an AR having never owned one. I have read all the reasons why I should avoid the AR/DI platform like the plague. The more I've researched tho, it seems to Me that the contemporary lineage of AR's suffers from a hasty generalization of past and present anecdotal evidence. Modern DI AR's just work and reliably so. Heck of alot more affordable too! "

You got it right. A lot of the "stories" surrounding ARs are bullshit and myth. Buy a quality AR, run it wet, and you won't have a problem.

Anonymous said...

I despised my M16 in the desert for its lack of range and reliability. For a rifle-range plinker AR, however, I won't spend the extra cash for an add-on piston system.

Go buy a Sig or Steyr AUG if you think that piston is going to save your life during the apocalypse.

Ed Foster said...

I had to do a destruct test on a piston system up at S & W a while back. It was from one of the biggest names in the business, and it shattered the ass end of the lower reciever in an amazingly short time, while giving extremely erratic ejection. If anybody wants a copy, I'll cheerfully forward it.

The AR15/M-16 has a piston, and it's a really good one. It's called the back of the bolt. That's why there are gas rings there.

The bolt is only cammed open by the rearward movement of the carrier. The carrier (cylinder) is forced back off the bolt (piston). Kinda like those old WWI rotary engines where the pistons were fixed in place and the crankcase rotated.

The piston is on the same centerline as the bore, and has almost no camming effect on bolt movement.

Smart Mouth in the back of the classroom is waving his hand and screaming "There's a side load on the gas key".

Yes there is, and it's only a matter of a few ounces, on a long flat surface that shows virtually no wear after the designed 10,000 round life cycle of the upper. So what?

Bottom line, less mass being accelerated to unlock and cycle the bolt assembly, less camming (no piston offset) against the bolt means less lateral bolt displacement and less drag.

Plus, the piston and bolt are the same part, simplifying everything. And the tail on the bolt keeps everything in much better alignment than a conventional piston, which means less wear and, again, less drag.

Look. I work for Continental Machine, which is also Stag Arms. If you want a RHINO-type piston system (RHINO was the first to crank out the external piston system back in the '60's), our SKS type set-up is better than most anything else I've played with.

The lug replacing the gas key is milled integral with the bolt carrier, the system is timed rather well for spring weights and cycle time, several good things.

But nobody in the business makes a piston system because it works better. They don't, any of them, something the army proved in exaustive testing several years ago out in Fort Collins.

They try to make the best piston system they can, for people who have been told they need one. But you still have peening or spalling where the op rod contacts the bolt carrier, and you still have the same amount of gas being used to move much more material over a longer period of time, while reducing the specific impulse being delivered to the bolt assembly.

The Ljungman family of rifles was used from the arctic circle to the Egyptian desert with superb reliability. That's why Stoner decided to use it's gas system, rather than the conventional one he used, with much poorer effect, on the AR-18.

That ejection port is a hell of a lot better gas vent than a bitty hole under or over the barrel, especially when the "exaust" is being mixed with all the fresh air being sucked back and forth by the bolt.

For reference, the upper runs a lot cooler than the lower, which is why the hole in the upper's rear lug is .250 high, but .270 long. It allows the lower to stretch in full auto without binding the upper.

If you want one, we'll sell it to you. But don't expect it to work as well or as long as the smoother and much less stressed traditional AR system, because it won't.

If you find that difficult to believe, then Dude, you're smoking much better shit than I am.

Außenseiter said...

To shoot?

I can shoot a CZ-527 too. More accurate per € than any AR platform. More reliable too.

Joel said...

Personally I prefer a .30-cal, and I do enjoy joshing friends about their poodle shooters. But yeah, a lot of the talk about AR reliability, while maybe not quite myth, is based on stuff that happened in the '60's and is just no longer true. And I've had my ass handed to me by enough AR shooters in high-power matches to respect how accurate they can be.

My own day-to-day carbine is an AK, but that's just because it was (FAR!) less expensive and personally I consider the fact that it's ugly as perverted sin to be an asset. In fact I deliberately uglied mine up. I want people to wonder, "Just how crazy IS this guy?"

Since getting used to it, my only real objection to ARs any more is that they seem kinda...precious.

Tam said...


I own... oh... maybe forty crank-cockers of some variety or another, from a Kar.71 to a custom heavy-barreled Mauser in .300 Whisper. A few .mil self-loaders, too (although I sold my SVT-40.)

None of them really fill the niche for which I own an AR carbine. I certainly can't imagine running the course I just took with my Garand. Maybe my Vz-52, but it would have been awkward.

Anonymous said...

The internal magazine of the Garand qualifies as a "real mag"?

Tam said...

I think he was talking about one of the ones converted to take box mags. Or maybe the BM-59.

Ed Foster said...

For anonymous @ 2:03 p.m., I'll call B.S.

No, I wasn't there, but lots of people I know were, all people who saw the elephant, and I had my turn 40 years ago with an earlier and theoretically less evolved version of the same weapon.

Plus, I more or less personally kept a platoon of Connecticut reservists in parts, shipping to Afganistan whatever they needed from Stag Arms/Continental Machine. They had no supply sergeant, as he managed to get himself arrested shortly before deployment.

About the only high wear parts were the charging handles. Specifically the latch spring, and that was something that failed in the grit quite gradually.

Along with the Connecticut kids in support of the 10th Mountain, I also have a 5 tour SEAL buddy (1 in Afganistan, 4 in Iraq) who never had or saw a single weapon related stoppage. Not one.

Occasional beat up magazines, some ammunition old enough to vote, but nothing intrinsic to the weapon.

Another friend, a Captain in the Air Force, teaches the Designated Marksman course at Benning. If there was a problem, he would hear about it hours after it surfaced.

I've made my living for 20 years with the M-16/AR15, at Colts, S&W, and Continental. I've signed off on more than a million of them, and there isn't another hand held weapons system on the planet that uses NATO cartriges and a box magazine that is as reliable, as accurate out to at least 500 meters, or has natural ergonomics as good.

Every lot of 100 rifles has two weapons pulled at random, and fired 6,000 rounds each. Those Government inspectors aren't easy on the weapons, and the entire lot is failed if one of the M-4's or A-4's gets 5 stoppages in 6,000 rounds. More than willing to quote the DCAS spec and let you look it up.

For reference, most lots go clean, and more than 2 stoppages is practically unheard of.

Anonymous said...

Außenseiter, it's all about tools in the toolbox. More tools is better - my AR is a superb self defense rifle and is great for coyotes raiding the hen house. Better than my Scout rifle or my FAL? Yes, just as my hammer is better for driving nails than drilling holes or sawing boards.

Al T.

Ritchie said...

Just for idle amusement, look up the price of BM-59 mags.

Neutrino Cannon said...

Not just the bolt carrier that needs redesign when you go gas piston. Ever notice how most of the gas piston ARs have different gas blocks? Turns out the original AR gas block doesn't do so well if there's a piston smacking back and forth inside it.

James family outpost, Iowa. said...

I like the direct impingement design for what it is. I found it hard to clean, but I liked it. I did sell my AR though, and now my only .223 is a mini-14, it suits me better.

Tam said...


Having owned an AR-70, I'm hard to shock. ;)

Bubblehead Les. said...

All you kids with your new-fangled guns, why none of them are worth the grease it takes to keep a fighten gun runnin' like the old... (Brown Bess,Mississippi Rifle, 1861 Springfield, Trapdoor Springfield, Krag-Jorgenson, 1903 Springfield, M1 Garand, M14 and M16).... that we used to use in MY day! Look, Uncle Sam picked the M16 family as the weapon to use over 45 years ago, they ain't walking away from the 5.56 Nato round, so we all might as well just get used to it. Good thing about most of the Free States in the U.S. is the fact that no is forcing you to buy an M16/M4 with or w/o a single stroke on top, so shoot what you want and can afford. Just keep in mind what it costs to feed the weapon you use, and can you afford the price of its ammo? Then go have fun.

perlhaqr said...

Doesn't a gas piston on an AR lose you the entire "fully floated barrel" advantage it has over the AK and FAL (etc etc) ?

Tam said...


"Doesn't a gas piston on an AR lose you the entire "fully floated barrel" advantage it has over the AK and FAL (etc etc) ?"

That, and it adds reciprocating mass above the bore axis.

Neither is that big of a deal in a fighting rifle, of course, but it has an effect on the freaky accuracy potential (for a self-loader) of the platform.

Außenseiter said...


Wouldn't an RFB fill that niche? It looks very ergonomic and with a muzzle brake it probably doesn't even recoil that hard. Prettier in any case.

@Bubblehead Les
Isn't a Steyr Aug a better choice than the Ar-15?

og said...

I know the ultrasonic tanks the big shops use to clean guns do a bang-up job on impingement AR's, I wonder how they handle a gas-piston.

Tam said...



1) 5.56 from a short barrel indoors is bad enough; I have no desire to experience .308 muzzleblast inches from my face indoors.

2) Like all bullpups, reloads are a slow, awkward, fumbling process, unlike the poodleshooter, whcich can be topped up or refilled while keeping the muzzle and eyes.

"Isn't a Steyr Aug a better choice than the Ar-15?"

Of the two countries large enough to issue both the AUG and their own postage stamps, one eschews conflict and the other issues the Armalite to its SAS and other specops types who may actually need to bust caps. Taking military rifle advice from the Austrians is like taking condom advice from a virgin.

Tam said...


"whcich can be topped up or refilled while keeping the muzzle and eyes." should, of course, read "which can be topped up or refilled while keeping the muzzle and eyes on target."

As an aside, you keep saying things like "Prettier in any case," and "Ugly as sin," and I keep wondering what looks have to do with anything. If you want pretty, buy a picture. I don't choose my tools based on their looks. Form follows function, and all that.

Anonymous said...

>>What's the whole point of AR's anyway?

They are like Barbie dolls for grownups. You can dress em up any way you like.

MIne is currently Clovis, CA Barbie. With a pinned magazine, chambered in 6.8 SPC

Bram said...

Joel / Ed:

Call BS if you want. I was there in '90-91. Relatively new, very well maintained M16A2's jammed constantly in the Saudi desert. Not just mine - every rifle in the company when we went to the range. Maybe that is a unique environment but it damn sure happened.

Anonymous said...

Bram, 14 months in Iraq here. 4th ID soldiers I worked with, no issues. What we thought worked (keep your AR dry)in the old days has evolved to keep your AR wet in a dusty environment. Hate to be snarky, but your rifles were not well maintained if they wouldn't run. Your experience from 20 years back is not very valid.

Al T.

Tam said...

On this point I'll throw out the historical note that the M1 Garand's initial nickname was "Jammin' Jenny" and they, along with Thompsons, BARs, and everything else, malf'ed left, right, and center in the volcanic sands of the Pacific. ;)

Bram said...

4th ID:

1. Telling an infantry company of Marines who clean their weapons several times a day that they don't know what they are doing is dangerous.

2. We were told very light CLP and generally followed the instructions. Dry, wet, whatever, didn't matter in Saudi. The Brits had the same problems with their shitty bullpups. The Saudi's guarding the range with their G3's thought we were all pathetic.

3. From what I've seen, the fine sand changes to bigger particles farther north you go.

4. I would never use CLP in a combat zone again. It mixes with sand and turns to glue. Synthetic like Miltech is the way to gp.

5. I still wouldn't pay extra for a piston AR for range plinking.

Tam said...

Having owned and maintained more than a few decidedly unmagical HKs in my time, I'm curious what the Saudis were using for lube.

There's nothing to a G3 that should give it any special edge in reliability; its roller system is not much less cack-sensitive than the multilugged AR bolt lockup.

Ed Foster said...

Go back to the blog header of two or three days ago, titled "Sigh.
Now I have to clean guns".

Everything is there that I've learned about lubing the M-16 series since Camp Pendleton in "66, and it works better than anything else you're going to find.

Give it a try. Bobby and his buddies in Afganistan ran their rifles that way ( I sent them over a pound of LubriPlate 120-A) in a savagely dusty environment without malf one. Slick as snot.

Bram said...

Tam - Not sure about the lube. The Saudi's seemed happy enough with them and their little MP5 brothers - besides being heavy as hell. (Most of the Saudi soldiers I met were fairly big guys.) That big bolt seems pretty robust.

They are now replaced with Steyrs - read somewhere that the FAMAS was a close second in trials.

Anonymous said...

At this point in the game, I guess I'm off topic, but have a Stag piston AR and for me the main benefit is it's so much easier to clean. Having had to clean the M16 in every variation from the A1 when I first enlisted to my current M4, the cleaning has always been a thorn in my side.
Thus far the Stag is as accurate and dependable as the M4 the King lets me use, and like I said WAY easier to clean.

Tam said...

Anon 1:30,

"At this point in the game, I guess I'm off topic..."

Thirty-something comments in, I'm lucky if I remember what the topic was in the first place, and I wrote it. ;)

Billy Beck said...

"Gas piston"?

Don't that make it an AK-15?

Außenseiter said...


I think I've seen guys reload bullpups without moving the muzzle of target. It's doable, I think.


If he had more experience, he could likely reload without having to look what he's doing.

BTW, with the RFB, isn't it easy to use a supressor? And even then, it'd be likely shorter than a AR-15 rifle while firing a more powerful cartridge..

@Tam, last post
Everything else? Even the 1903 springfields?

I kind of wonder why it took so long for the AK to appear.

Tam said...

"I kind of wonder why it took so long for the AK to appear."

If the AK were as reliable as the internet thinks it is, everyone would use them.

If it were as inaccurate as the internet thinks it is, nobody would.

Kristophr said...

I think we need a better rifle, not a kludge.

Somethin' new. Surely someone can design a self-loader with an AR style free float barrel, and a piston operated bolt + carrier?

Use an annular ring south of the gas block to vent excess gas? That way the piston and gas tube does not have to ever contact the barrel gasblock.

Außenseiter said...


I'm sure it's reliability has been extensively tested. Maybe there are some videos of various tests.

Accuracy wise, it's what, 10 MOA? Good enough for infantry combat ,probably., especially if you have lots of ammo.

Tam said...

I don't need go searching for internet videos, I've owned a half-dozen of the things and fired dozens more.

Außenseiter said...

So, why do you say it's reliability is overrated? Many guns won't fire after having dirt thrown inside them, or after dragging them through mud, that kind of thing...

Kristophr said...

My wife got her's to malf with Chinese lacquered ( more like rough tempura ) faux hollowpoints.

It can be done ... I watched it happen.

The instructor was delighted to have a real AK malf to train with, and bought every last bit of that awful ammo from her.

Tam said...

"So, why do you say it's reliability is overrated?"

Because I've seen way too many of them choke on a perfectly clean firing range, Außenseiter.

This is not a great big theoretical "my friend said", "I read it on the internet" thing here.

Are they more reliable than an AR? Yes, somwehat, for a given value of "reliable". Will they stand up to the abuse and neglect claimed by internet commandos and counterstrike kiddies? Fuck no.

Unknown said...

All rifles suck. I've not yet seen one that didn't have several sucky misfeatures on or about it.

The sheer number of 'improvements' out there, ranging from handguard designs to replacement operating systems, should be a warning sign of how imperfect the AR15 is.

However, they're not all bad ideas; and since all rifles suck in various ways (and different people have different but valid opinions on what constitutes an misfeature sufficiently aggravating to warrant replacement); one valid approach is to evolutionarily change the AR15 platform into something better.

Much like you, I think it's misguided to attempt to fix the AR15... but that doesn't mean that adding a piston to the AR is inherently bad.

The PDS does seem to solve a lot of my objections to the AR15 (charging handle location, no folding stock, hot fouling in the action); yet retains compatibility with a lot of the nice whizbang doodads that make accessorizing so much *fun*!

That said, I've come to the conclusion that if I just want to accessorize I'll get a 10/22 in a Nordic Components clamshell reciever and hang all the AR whizbang accessories I want off *that*.

For serious use, so far I'm sticking with my ratty and crooked AK which feeds & fires until the end of days and will still knock down bowling pins at 100 yards if I do my part. I'm willing to trade it in if an ACR/XCR/SCAR/RFB demonstrates itself to me personally to have superior ergonomics, equal reliability, and be enough of an improvement that it is more than the improvement which would be brought about by spending that money on practice ammo.

Suburban said...

After breaking pins off my first PRI barrel wrench (a tough little unit), I put a 4 foot long pipe over the breaker bar, and finally got the barrel nut of my RRA 9mm upper to come loose with a crack. So I'm not eager to buy anything ASSEMBLED by RRA again soon. The gorilla that assembled my upper may still work there.

There's probably a reason that we have, what, millions of Direct Gas Impingement rifles in this country. I was going to write, "I hope that someone comes out with a FAL in 5.56mm, or maybe a 5.56mm M-14."

Then I remembered there is a 5.56mm M-14. They're called Ruger Mini-14s, and I don't see much of them, even now that you can get good, factory, 20 and 30 round magazines for them.

There was a .223 FAL rifle, but there were problems with it, and it never got fixed and put into full production. Maybe there's a good reason why that is.