Rock River Arms PDS Carbine

I recently blogged about RAA’s PDS pistol. This is the carbine version of the pistol.

The Piston Driven System Carbine utilizes a propriety bolt carrier that actuated by a piston. The return spring is located above the barrel, much like the Para Ordnance TTR rifle, rather than the rear buffer spring. This eliminates the need a buffer tube, allowing a folding stock. Unlike the Para TTR the PDS does not have a traditional AR-15 charging handle and instead has ambidextrous forward H&K-esque charging handles.

Gas block and charging handles
Caliber 5.56mm NATO
Upper Proprietary PDS upper
Trigger RAA two stage
Grip Hogue Rubber Pistol Grip
Barrel 16” Chrome Moly, 1:9 twist
Stock RRA Side-Folding 6-Position Tactical CAR Stock
Total Length (stock unfolded/extended) 37.75 inches
Total Length (stock folded) 26″ inches
Weight 7.4 lbs
MSRP (Price) $1685

Steve Johnson

Founder and Dictator-In-Chief of TFB. A passionate gun owner, a shooting enthusiast and totally tacti-uncool. Favorite first date location: any gun range. Steve can be contacted here.


  • SpudGun

    This should sell well if only for the ‘folding stock envy’ of the AR-15 crowd. Why the vast majority of shooters need a fold stocking is a completely different conversation, but hey ho, to each their own.

    At least the carbine is a more sensible and practical design then the ‘pistol’ and if I got a PDS Carbine free in a box of Corn Flakes, I’d definitely give it a go.

  • DavidR

    I really like how this design highlights the flexible modularity of the AR design.

    I’ve said it before and I’ll say it again. It will take a revolution in ammunition to even *threaten* the AR design with obsolescence.

  • I’d rather purchase the pistol for a variety of reasons, all of which are related to Canada’s bizarre gun laws.

  • CharlesA222

    The lower handguard is kinda funky-looking. This is definitely the best (between this and the Para TTR) realization of a piston-enabled M4…ditch the hybridization of designs that really aren’t complimentary, and keep the best of both worlds.

  • Josh

    I like it, but where is the bayonet lug? Where are the sights? Why can’t I mount a sight all the way at the foreend of the rail to increase my sight radius. If I have to spend close to $2000 I want a bayonet lug to mount my bipod on and decent sights. I am not going to spend that much money and buy a new bipod too, forget it, I’ll keep what I got. When they come out with a better designed weapon system give me a call until then don’t waste my time with overpriced junk.

  • toadold

    If you have ever tried to carry a rifle to a shooting range on a motorcycle you would understand the wish to have a one you could fold up and conceal in your luggage. A rifle that you can carry in a tennis racket bag in an urban area is also desirable. If you have to get in an out of a car or other vehicle and you want to have a rifle with you that is ready to go with one move then the folding stock starts looking good. The PDS carbine gives you a longer barrel than an M-4 but gives you at least a comparable package in overall length.

  • Ivan

    One of the greatest modification of AR design I think.
    How are you think, is it possible to mount a buttstock on back rail in Pistol version?

  • Lance

    Promising idea…. Except FOR THE LOUSY G-3 charging handle. One of the best AR features its its charging handle and they replace it with one of the worst designs for a charging handle in fire arms history. I think Rock River needs to know right gas system but change some features on it asap!

    Another change is remove the cheap M-203 hand guards for the forend. A good tri or quad rail is needed.

    I find every AR maker making a Piston AR now. I think everyone is eyeballing the M-4 upgrade competition coming in the next few years and every one wants to ride the tidal wave. Eh… Steve?

  • jdun1911

    That’s a M4 stock not CAR.

    Bayonet lug doesn’t work on a 16″ barrel unless the bayonet is modified. A modified bayonet will run over $150 the last time I checked.

  • jdun1911

    I forgot to point out that unless it is a mid length 16″ barrel you need a modified bayonet for 16″.

  • drewogatory

    I actually like this design, but the day will never come when I need a 16″ 5.56. Seems like alot of money for a plinker.

  • jeff from CA

    It’s a shame they put a buffer-tube style side-folding stock on this picture.

    Is the H&K style charging handle a necessity of the design? Is it reciprocating? I’ve always found the AR charging handle awkward. You have to lower your gun significantly to operate it, or reach under and press back on the right-side latch with only one finger.

  • Martin

    I, for one, and glad it isn’t covered in rails on all sides. This handguard doesn’t exactly thrill me, though.

    I don’t like the fact that is has no sights. There’s something wrong about paying $1700 and not getting sights.

    And on the subject of those 1700 dollars, why are all piston guns double a decent AR? Is it just a fad tax? Yeah, yeah, I know. The bolt and upper are different, but the barrel and lower aren’t. I can understand some added cost, but not double.

  • DaveR

    As an aside, can anyone explain to me why the AR15 charging handle is often hailed as being so great? I know that a lot of folks are **used to** where the AR CH handle *is*, and I know that it’s a serious step-up from the bolt-mounted, reciprocating CH of the AK, but it still seems like it’s a compromise that came about b/c of the DI mechanism of the AR.

    To my way of looking at it, the AR15 CH is the AR’s weakest structural component, and it’s in the shooter’s face too. If the shooter forgets to close the CH after locking the bolt back, it is easily bent and this can completely brick the gun. Also, the CH requires that the shooter *significantly* shift his hands from the firing position to cycle the bolt; this also requires that the shooter must break his cheek weld.

    A forward mounted CH just seems to make the most sense, given the nature of a fighting rifle.

    (And Lance, this is not directed at you–though I’d love to hear your reply–but it’s just that I’ve heard other people say this about the charging handle and the advantages are not obvious to me. I’m happy to learn something here.)

  • TCBA_Joe

    I’d love to get my hands on one.

    A few issues I see from these stock pictures:
    Needs a Tri-rail handguard or a modular style handguard that accepts rail sections.

    Rail needs to be expanded out to the end of the the rifle over the gas block. (I’m trying to figure out why there’s picatinny rail on the bottom of the gas-block, but not the top).

    Exposed c-clip on the outside of the rifle? Thanks, but not thanks. No reason such a small retention part should be on the exterior of the weapon.

    I can’t tell, but it looks like the charging handle folds down against the side of the gun. I’d think for ease in use it should be angled off the rifle in order to facilitate manipulation of the charging handle.

    I like the concept. Still has a little maturing to do for market appeal to certain (large) segments, but I think it has potential.

    Lance, I’d respectfully have to disagree about the charging handle. Most modern rifle systems have a side-charging style charging mechanism. While the forward style G3 handle may or may not be superior to other positions (FAL/AK side, or AR rear), it is not a weak point.

    Is this short or long-stroke piston?

  • Please, RRA, pretty please, make your 308 rifle available with the piston system.

  • Stella

    Another “why not the 1:7” product. For the price more barrel options ought be expected.

  • Big Daddy

    It looks like a great idea and probably works very well. BUT… also looks like after they made this nice piece of machinery someone from 1955 decided to design the rest of the rifle.

    It has a definite 1950’s NATO look to it. Maybe that was done on purpose???????????

    The handguard, the charging handle, the cumbersome looking device for the stock. It kind of says 1950s NATO to me.

    It does not look like a rifle made in 2010 considering all the stuff on the market these days for AR rifle.

    I wonder how it shoots and if they make a full auto version.

    The para ordnance AR is also a funky looking rifle.

  • Lance

    @TCBA and DaveR

    the advatage of the Oringal AR CH system is that its close to you and is ligt in pulling back. Yes its near your face but its designed to be close to get to in a hurry. The H&K design is horibble it awkward with its hadel going flat to the reciver when not in use and you have to grab it in a hurry can lead to it slipping from your finers easly. It also have a long and heavy pull and its not we to small shooters who have a hard time racing and pulling it to ther rear.. The M-14 and FAL had better systems than HK in the battle rile arena. The design is good for RRA but a FAL or a closer handle like on a M-14 would be alot better.

  • Aurelien

    “Is the H&K style charging handle a necessity of the design? Is it reciprocating?”
    Non-reciprocating charging handle.

    RRA says more stock and barrel options will be available as soon as the end of the year, as well as tri-rails handguards for both the pistol and the rifle.
    This is just brand new, dont start yelling it has no modification options when the RRA docs clearly state they would be available in the near future.

    I think the folding stock is gonna be a big plus when the rifle is available with a fully adjustable sniper-style stock.

    As fot the bayonet lug, i dont believe a law enforcement/civilian rifle like this one really needs one. Even the military (except the brits) dont use bayonets for combat anymore.

  • Nadnerbus

    Ivan, I’m pretty sure the answer to your question is “federal felony.” I wouldn’t mount anything more than a sling stud there or you are asking for trouble.

    “Exposed c-clip on the outside of the rifle? Thanks, but no thanks. No reason such a small retention part should be on the exterior of the weapon. ”

    I didn’t catch that. Good point. That thing is just asking for trouble, and surely they could have come up with a more robust way to retain the pin.

    It looks like the top rail thins out over the gas block, which probably explains the lack of 1913 cuts. Would have made the part too weak.

    Bayo lugs are kind of anachronistic on most modern carbines. I like mine, just because it makes my Senator have nightmares, but I’ve never used it. Don’t mind that this one lacks it.

    I like the charging handle, and think some options for the hand gaurd would be good. Isn’t the return spring inside the hand gaurd though? Also, the rail seems higher due to the piston system. How does that affect sight alignment/cheek weld with the stock and standard hight irons? less of a concern with optics.

  • TCBA_Joe

    Nadnerbus, no problem with putting a stock on the pistol. As long as NFA laws are followed.

    I also don’t think there will be much problem with the high rail. The OBR/OBR-556, SCAR, HK416, and others have a higher sight line above the bore. There are companies making lower folding BUIS for these higher rails now. I believe Troy is one of those.

    I hope they start selling the folding stock assembly as a seperate part. The only ones I’ve seen available 3rd party for the AR seem less than sturdy, and because folding stock ARs are not common, developed for .22s.

  • The Para TTR is not a piston gun, it’s still a DI gun.

  • Mike

    Hopefully they create a 9mm version (or at least an upper) as a PDW alternative. That could give the MP5 a run for its money.

  • Big Daddy

    I carried a G3 for some maneuvers we did with the German Army and I hated the weapon. The charging handle, the hand guard. Even the pistol grip, it would pinch the skin between my thumb and index finger.

    Not to mention it was front heavy and you could feel the bolt travel. It was not a fun gun to shoot at all. Plus even the sound of it was weird. A blam blam blam you could hear the bolt moving and feel it too.

    I liked having a heftier weapon then the M-16 though, I really liked my M-3 grease gun best.

    If the rifle works well all the other stuff can be fixed. The lack of a rail over the gas is kind of obvious. If you have anything mounted there it will impede the ability of your hand to operate the charging handle. It is a bad design for a few reasons.

  • Ivan

    Nadnerbus, oh, I forgot the US laws. Yep, sadly truth… but buttstock asking for this place by him self! Sorry if I provoke someone.

  • jdun1911

    The people like the G3 probably never hump one for a long period of time. Of the three major battle rifles in that era it is by far the worst. The ergo and recoil pulse is horrible.

  • wizemanful

    I wonder how comfortable the charging handle will be. When I try to act out grabbing it, it seems a little far away. Of course, only holding it will tell.

  • Slow

    The laymans acr! Lol

  • Folding stocks are for people too dumb to know they really want a bullpup.

  • Peter

    I don’t like the h&k charging handle I have a cetme and the chargeing handle sucks you have to reach have way up the barrel and pull I back i think they should have used a ACR style cargeing handle

  • W

    the G3 is a fine weapon and comparing one to a M16 is faulty. for one, the G3 is a battle rifle: compare it to a M14 or FN FAL. Second, with proper training and familiarity the G3 is accurate and effective and i had no trouble with ergonomics. What a interesting AR15 design nonetheless! I cannot say the G3 charging handle would be any worse than the AR15’s 🙂


    The rail should go up furthur……I dont like the charging handle….theres no bayonet lug……..Im going to have to reach alllll the way up the 8 inch barrel to get to the charging handle……theres a exposed c clamp…. dont put a stock on it youll immediately get sentenced to 20 years…..the rail is will throw off my 2000 meter sniper shot with the 8 inch barrel….why is there a rail under the gas block but not on top…. it looks like its from the 50’s, why does it look like its from the 50’s…

    • TJ

      When was the last time you fixed a bayonet? A bayonet will also put your 2000 meter shot off. That exposed “C clamp” is a C clip style retainer. Don’t be a moron!

  • Moo

    I just got the carbine version. I would have liked to be able to engage the bolt retaining pin with my index finger of my trigger hand, I like the short stroke on the charging handles and agree a bit me under/ side barrel rail would have been great. RRA gives you a “lifetime” guaranty so I would guess they will stock parts for a while. I’d love to find a vid on complete breakdown of the system ( I learn quicker with tapes) I put a set of Troy Micro flips on mine for now. I’m not sure if I want to get a co-witness red dot or a range finder scope.

    I think if you give this PDS (Don’t forget there is no possibility of carrier tilt) a chance you’ll find it isn’t a bad system.

  • David

    I think it is a very neat looking rifle, myself.

    I like the fact that the bolt is attached to the piston, and the bolt has three massive lugs.

    The charging handle though, does bother me a bit.

    Not because it’s so much forward of the support hand, but because it folds down.

    If a magazine fails to lock the bolt back and if the handle is folded, you have to flip the handle out to charge the rifle.

    In a high stress situation thats just too many motions.

    I would like to see a strong fixed charging handle.

    I still like the rifle though.

    Maybe a coat of NP3 on all the internals and a barrel rifling of 1:7, you’d really have a nice weapon.

  • Moo

    I’ve had mine for a few weeks now. My only complaint, kind of, is the rail. I put a troy swivel there. I tried a v grip/bi pod but it would not fit properly. But then again I don’t like “lights” kinda like screaming “Shoot over here” and the extra weight of accessories reduces swing time. The ambidextrous charging handle I like. I can stay on target without taking my hand off the fire control on either the strong or week side. (I never cared for the gis charging handle being in the back.) It shoots well for a 16″er and recoil (even with 62 grain 5.56) is softer than Charmin. But as the man said “to each their own” This piece will work for some and be hated by others. Me, I like it. There were a few things they could have improved as it truly is not an AR15 because it is so proprietary and cannot be interchanged with other receivers.