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Adams Arms builds a kit to convert your AR-15 rifle from direct impingement (a.k.a., the “shit where you eat” system) to clean-running piston-driven bliss (schematic above). The company’s carbine length system runs $379, and they reckon there isn’t an AR made that doesn’t need to make the switch. To that end, Adams Arms has just raised $2.7m in funding from the investment bankers at Littlebanc Advisors. According to the resulting press release, “The capital raise will enable Adams Arms to support increased demand from its distributors, dealers and OEM partners, including Brownells, Midway and Smith & Wesson.” Both Adams and Littlebanc are both based Where the Sawgrass Meets the Sky, giving further impetus to those who call Florida the “Gunshine State.” Without sarcasm or irony I might add. [Make the jump for the rabbi’s epistle to Eric on the advantages of a gas piston AR—which don’t necessarily apply to a converted AR. h/t David]

 “A piston AR has the advantage over a direct impingement AR in that the hot, dirty gas that gets bled from the barrel and fed into the receiver to cycle the action in a standard AR is replaced by a piston.

With a piston, none of the hot, dirty gas enters the receiver which keeps it cleaner and cooler which extents the life of component parts.

The drawback of piston ARs is that the piston hits the carrier above its line of travel which creates a angled, downward force on the carrier known as carrier tilt. Manufacturers mitigate the tilt by increasing the size of the end of the carrier to limit its movement, but the force and friction is still there.

The advantage of the SCAR [over a converted AR] is that it was designed as a piston gun the piston hits the carrier in the line of travel (eliminating any carrier tilt).”

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  1. Piston ARs are a (poor) solution in search of a problem. If you want a piston gun, get one that’s designed as one from the beginning.

    • Wrong. All of the ergonomics and modularity of an AR, plus the reliability of a superior gas system = pistons FTW.

      Note that Stoner himself never again made another direct impingement design and the assault rifles of most Western nation’s militaries do not use DI.

      • Firstly, the AR is not a true direct impingement system; the gas does not impinge directly upon the bolt face to facilitate cycling (and if it did, considering the bolt rotates to lock, it would result in sheared lugs and a FUBAR’d barrel extension). The AR bolt has piston rings (gas rings) on it to create a seal for the expanding gases as the gas fills the chamber in the bolt carrier, while the various holes in the carrier itself act to vent out excess gas to keep the pressure from getting too high too fast. Once the pressure reaches a certain point, the carrier moves to the rear (acting as a movable cylinder, the bolt being the stationary piston), unlocking the bolt, and allowing the weapon to cycle.

        The force of the expanding gases INSIDE the carrier are what facilitates cycling, eliminating the need for an actuator rod (“piston”, or op rod).

        AnotherMatt is right. Shoving a piston in an AR-15 is a solution looking for a problem, and often creates more problems than it solves. The AR-15 is reliable (and proven, with the current wars) without the need to change the operating system.

        Secondly, other nations’ service rifles are not designed as the AR-15 is designed. The manufacturers they purchase from build their rifles the way they are used to building them (with actuator rods), which furthers Matt’s point: use a rifle that is built from the ground up as a short-stroke or long-stroke piston system.

        • Dont get me wrong, there are excellent gas piston designs, such as PWS, though the traditional design is still very reliable and effective.

          If you want a gas piston, go with a SCAR or other design. Ill gladly pit any of my noveske or LMT Ar15s against a competing gas piston design.

        • Dont get me wrong, there are excellent gas piston designs, such as PWS, though the traditional design is still very reliable and effective.

          If you want a gas piston, go with a SCAR or other design. Ill gladly pit any of my noveske or LMT Ar15s against a competing gas piston design.

  2. The “problem” is – How do we bilk more money from AR fanboys who have a bunch of AR type guns and more money than sense?

  3. Ran an Adams Arms piston conversion kit on my old Sabre Defense carbine. Works great and support from AA has always been great!

    • I have to brag on AdamsArms, they make a very professional setup, and they offer a very fair discount for military (active duty, retired, and veterans). Not many companies willing to do that for us today

  4. on a clean, well lit range in a temperate climate the ar is quite nice. i believe the term is ergonomic. but it’s to labor intensive and has too many fiddly bits to be trusting your life with. as many of us that could scrounged up pistols to back up our m16’s with because wwe had no faith in them. and from the new’s clips from the sandbox that appears to be true today. a lot of the guys are packing sidearms with their m4’s

    • The M-16/M-4 is a government issue rifle. No doubt they save money by eliminating the cost of the piston assembly…

      • Couple points:

        The AR15 has a proven track record. If soldiers are too lazy to provide proper maintenance, they are asking for problems.

        The AR15 platform long before a piston system was in place. The government is not “eliminating” the piston,it was never there to begin with.

        Please get your facts straight.

        • If soldiers are too lazy to provide proper maintenance, they are asking for problems.

          Yea, because if you’re stuck in the desert / jungle / other hostile conditions surrounded by enemy forces, you really have the time and means to take apart your weapon and spend a couple hours cleaning it….

        • totenglocke, you dont need a “couple of hours” to break it apart and clean it. Lubricate it and it will serve you well.

        • “If soldiers are too lazy to provide proper maintenance, they are asking for problems.”

          I love this retard comment. I guess all the numerous times my M16 crapped out on me in the Middle East, during training and at the range, it was because I was too lazy to clean my weapon. I guess it had nothing to do with the weapon at all. I’m such an idiot! And to find out from all of these internet armchair commandos that it was my fault after all, because I should have put a few hundred MORE hours into weapons maintenance than I already did.

          Try this one out. You carry this weapon on your belly, under fire, at night, through the sand, looking for mines along the way, breach some obstacles, then try to get more than one round off before your bcg gets stuck in your buffer tube because of the sand. Oh, then try to clear it under fire. THEN, come home so someone can tell you your “too lazy to provide proper maintenance” thats why your M16 failed you. What a joke.

          The truth is that the M16 or M4, or whatever you want to call it, is a substandard weapon for infantry use compared to just about every other rifle employed by all of the worlds military forces. It’s not the worst, but the only “proven track record” I have experienced with it, is that it’s a high maintenance, unreliable turd. If Stoner had developed the AR18 first we wouldn’t be having this stupid conversation. And many Soldiers and Marines would still be alive that died because they carried an M16 into battle.

          I served with USMC, Weapons Co. 1/5 as an 0351 and spent several years as a uniformed officer. This included SWAT and other “tactical” team duties.

    • so its too labor intensive to properly lube the rifle?

      The “DI” Ar15 is a extremely reliable weapon, even in harsh conditions. Its about discipline and care. Its funny how US special forces and navy seals continue to carry the M4, even with the HK416 and SCAR being available.

      The “lots of parts” argument also pertains to any other western rifle. The only little parts you should periodically check and replace during their service lives are the buffer spring, extractor, and extractor spring. With these parts in serviceable condition, good magazines, and proper lubrication (not CLP), the M4 is a very reliable and trustworthy weapon.

  5. I used an AA Piston setup in my last black rifle build. Works flawlessly. I have put well over 2k rounds through the rifle and beyond cleaning the barrel, everything else just requires a wipe down. Cleaning time is cut in half if not more. If you are not replacing parts from an AR and merely purchasing parts to build one, it really is not that expensinve. I got the package on sale for $290 from Brownells. If you figure in the fact that you are not having to buy a carrier or gas block as the package includes both, you are really only spending an extra $50-100 depending on how cheap you would have skimped on your carrier and gas block.

    • There is no “fix” for carrier tilt. The modifications will reduce the tilt movement, but the tile pressure and friction will remain

      • Carrier tilt? Try putting a couple thousand rounds through a decent piston AR. They absolutely smoke DI AR’s in terms of reliability. Enjoy your DI guns, it’s a free country. For heavy volumes of fire with minimal maintenance, pistons outperform DI guns.

        • 1.) most of the carrier tilt claims are bullshit. The solutions are very practical and foolproof i.e. primary weapons systems.

          2.) DI guns are “more reliable”? marketing bullshit. In fact a Special Forces study at Fort Carson found the Mk18 CQBR to be more mechanically reliable than the HK 416. go figure.

      • Glad you chimed in. Maybe you can explain what I’m missing then. My perspective:

        The Adams Arms looks like it is great for high rates of fire through SBRs (velocity numbers seem to indicate this–see Defense Review post above).

        I don’t see how it’s possible for any noticeable tilt to occur with the Heavy Buffer Anti-Cant and the Adams Arms installed because the carrier rides on the buffer during the entire stroke. The only way I can see it happening is if the buffer tube is improperly machined (i.e. out of spec). In other words, the same wear potential that a DI setup has.

        A friend of mine is a licensed class3 manufacturer and he has a registered SBR with the Heavy Buffers Anti-Cant buffer, Adams Arms carrier/piston kit, POF Roller Cam Pin, JP enhanced bolt, and PWS 416 Enhanced Buffer Tube (that has the extended buffer lower lip to “guide the carrier”). No wear on the carrier or buffer tube after 14,500rds during testing (he shoots repeated 900rpm, 150-rd mag dumps, which melted the gas tubes regularly on his DI uppers).

        Isn’t DI basically a piston with less leverage (gas travels further, shorter “piston rod” right on the carrier) making the carrier tilt issues inherent to both systems, although less pronounced in DI?


  6. I love how everyone claims “FANBOY!” when they hear piston ARs. There are problems with D.I. There are problems with piston driven. But wait, you guys are right. It’s impossible to replace operating systems. LWRC, Adams Arms, PWS, LMT, Stag, Sig, CMMG and Ruger must all be crazy. Sand and carbon never lock up bolts. Also, I read an article on MSN about how 65.123% of AK ‘fanboys’ demand a direct impingement AK…

    P.S. There is a solution to carrier tilt. It’s called apathy… or a lil RTV… you pick.

  7. I won’t debate the benefits of a piston vs. direct impingement, as I’ve never fired a piston rifle in my life.

    I have a tad bit of experience with the M16/M4. On nice ranges, and in Panama, Desert Storm, and OIF I, OIF 07-09, and OIF/OND 11-12. In Sadr City in 2004 I was in a two hour firefight in which I fired my 210 round basic load, 180 rounds I took off a wounded Soldier, and another 210 from my gunner (he was too busy on the M240 to bother with his M4).

    It is never a good thing when a Battalion XO fires over 600 rounds in deployment, much less in a two hour period. My rifle was almost too hot to handle, I could feel the heat coming off the barrel through my nomex gloves. I don’t know how accurate I was, given how hot the barrel was, and the fact that I was just a tad on the scared senseless side, what with all the dudes with AK 47’s and RPG’s shooting back at as.

    I had exactly zero failures to feed, zero misfires, and zero failures to eject during that firefight.

    The problems that “experts” at the gun shows, gun shops, and ranges all over the place talk about apply mostly to the M16 “A-nothing” originally fielded with almost no testing in Vietnam. There were issues with the original M16. Wrong powder, lack of a chrome bore, and the belief that the rifle never had to be cleaned. (Hence, not issued cleaning kits.)

    I will (hell I have) bet my life on the reliability of the M4 and not think twice about it. (As far as issued aluminum magazines…not so much, hence the seven MAGPUL magazines in my ammo pouches.)

    • If you believe the system is good and reliable, and I think your experience and those of others is proof that it can be, then why not move to an even more reliable system to further reduce the likelihood of malfunctions?

      Try one, you’ll like it. I love my AA mid-length upper.

      • Piston ARs run fantastic…right up until the piston spring breaks. At that point you have to remove the gas plug (hottest part of the gun) slide the rod out and replace the broken spring before the gun will work properly again. The DEA bought a bunch of LWRC guns to their specification half a decade ago or so. Apparently they had quite a few problems with broken piston springs. LWRC says they got better springs later and it’s not a problem anymore, but it’s a “single point failure” in the piston concept – it’s not true to say that piston guns are universally more reliable than Direct Impingement ones.

        I started out on the piston side of the aisle, then shifted more towards the Direct Impingement school of thought. To my view, there are two considerations when considering Piston versus DI: When you clean the gun (not when you lubricate it) how much time are you willing to take and are you willing to carry several more ounces in weight to shorten that time period. If you’re suppressing the gun, then there is little practical difference because the back pressure from the muffler will lead to almost as much junk building up in a piston gun as a DI one.

        • and that is the main problem with gas piston AR15s. They are not all created equal and most models don’t use interchangeable parts. Until the military adopts a gas piston model, spare parts will be more of a problem than with a DI gun.

    • I had nothing but problems with the M4 in the sandbox… when using CLP.

      My unit purchased a few other commercially available weapon lubricants for us to try and we found that quite a few of them made the rifles almost 100% reliable even with less cleaning than we were used to. Even the SAW ran well and those were notoriously finicky before.

      The M4 is a good system when properly maintained. CLP is crap in hot arid environments and needs to be replaced.

    • How hot do you think it would take the M4/M16 getting before you cooked a round off? How many rounds would you have to fire in what amount of time before you’d reckon (from your 600 rounds in two hours experience) the weapon would start to malfunction from heat?

      600 rounds in two hours works out to an averaged rate of fire of 5 RPM. That doesn’t sound like much to the average civilian shooter, but I can assure people that any hunting bolt gun, fired at that rate for two hours, would be too hot to handle – not just “a tad uncomfortable warm” to handle, I mean “you grab the barrel and burn yourself but good” sort of hot.

      I’ve shot even rimfires like a .17 HMR to being too hot to touch the barrel – and that took only 50 rounds in 10 minutes, or again 5 RPM.

      • I was plinking with a Mosin-Nagant one morning, 60 rounds in half an hour, and I stopped only because I could only hold it by the sling and buttstock. That’s only 2 RPM.

    • Thank you for your service to our country, sir, and for providing a big dose of reality to the uninformed. Your story is one I’ve heard from MANY vets.

  8. Here is some info: When my son was in Tal Afar, Iraq in the 25th Infantry Division he called home complaining about the CLP collecting too much sand for reliable functioning in his M4. I did some research and finally contacted Quantico Tactical (254-554-8940) near Ft. Hood, Texas. The lady I spoke to on the phone said that her husband had just started his second deployment, and that they had shipped about 50 bottles of a product called Slip2000 to his unit, because the soldiers in his unit had found it to be good in the desert during his first deployment.

    I sent some to my son and he said he liked it better than the CLP. I have not used it personally. I’ve got two Colt A3 models with about 1500 rounds through each of them with never a problem using CLP, but then I’m not in a desert environment.

    You can find the Slip2000 at if you are interested.

    • LWRC give buyers sample of slip2000 when you buy a gun from them. that stuff is awesome, one of the best gun lubes in existence IMO and experience.

      • Synthetic wheel bearing grease (i.e. Valvoline or Mobil1) seem to work best from my experience. Stays where you put it.

    • Slip2000 is awesome stuff, absolutely incredible.

      If you arent inclined to spend the money on a dedicated gun lube, you can do what my buddy does and use starting fluid to clean and mobile 1 synthetic motor oil to lube it. synthetic motor oil, being designed for internal combustion engines, works extremely well in the AR15 platform.

  9. As far as the DI vs. piston system, I have to go with LTC F on this one. I’ve not been in military combat with hundreds of rounds fired in a single day, but I do have other experiece as a LEO, including several rifle schools as well as qualification for everyone on the department four times a year since we adapted the AR in 1989. I’ve never seen a problem with the current system. If it ain’t broke don’t fix it. If I wanted a gas piston system I’d just by a rifle set up that way. Like the Lt. Colonel says, I think the bad rap that M4/ARs get is from the first M16 fielded about 44 years ago.

  10. point taken. the m16 i had didn’t even have a forward assist. next time i get to a free state i’ll have to check out the updated version.

  11. I own both DI and Piston Driven systems. Currently, my piston system is off for REPAIR, as it’s jammed-up from “not needing cleaning.”

    I Also own a 7.5″ DI gun which I built. I fired 350 rounds through it yesterday, with zero malfunctions. I would actually trust it over an AK-47 or any other firearm as far as reliability! Using Federal 62 gr, it runs like a champ.

    The AA piston upper does not mean “no cleaning required.” Quite the contrary. I learned the hard way that if you leave an AA piston upper in the safe dirty, it will gum-up and become 100% useless.

    I’ve left my Colt and Bushy ARs uncleaned, and while they were not 100% reliable after being dirty, neither of them required a GUNSMITH to repair.

    I’ll not be buying another piston upper. Period.


    • I own all three AK74,DI AR,and a Adams Arms upper Spikes Tac lower.There’s no way your DI is as reliable as an AK.All DI’s have gas rings and they are a wearable part much like brake pads on a car.Therefore they will need replacing.I hope you carry spare gas rings or your AR will become a single shot rifle.AK,s not so much there are reports from Iraq of original AK’s from the 50’s with shot out barrels still functioning.

  12. I just got an Adams Arms mid carbine, Ran 300 rounds through it the first day, not one problem. And have read most of the reports on di/piston systems. Stuff like the spring breaking on the AA piston rod causing problems, read the test reports, they removed the spring, and no, NO problems.
    The di systems have been in use for over 40 years, but that does not mean it is the best system. My first M16 in Nam, had no thumb assist, no chrome lining, and was told “ya don’t have to clean it”.
    I “fixed that first M16” after about the third firefight and had problems. Found a tree big enough to whack the hell out of it. The company armor said he had never seen one so banged up. The second one was better, but still not the reliability of the old M14, M1, M1 carbine. And the AK’s ans SKS’s….well tell them the di is better. They just don’t fail with all sorts of dirt, mud, water in them. Try that in your di with out a time out to clean it. The other side does not have that problem. Yeah, they were not as accurate as ours, but worked all the time.
    I bought a mini-14 because of the bad taste from the M16’s. Then got a M4 di system. It works fine, and I can say “it just don’t jam”! But, I am shooting from a dry, clean spot, clean ammo, clean mags, and all the time in the world to clean it. Now just got a Adams Arms upper (mid carbine) and can’t prove it yet, but believe it will run longer with out care and feeding than my di system.
    And the carrier tilt does not seem to be in vogue with their design, but I have ordered a anti tilt H3 buffer just to make my self a little luckier.
    I am not saying the di systems are bad, just saying I have seen and heard more problems with them than any piston systems. And, just because the current issue is one of di design, does not mean it is the best choice, after all they gave me no choice back in 1968. And the regular troops these days do not have a choice, so they HAVE to do with what they got. Special Forces, can choose. My SF nephew has sever M14’s issued to his teams. Just because,
    Just my 2 cents.

  13. People who argue the DI system is “battle proven and reliable” ought to listen to Jessica Lynch. Remember her? She was captured during the opening days of one of our Gulf Wars. The government had her fighting bravely with her M4 unti out of ammo??? She herself said she couldn’t stand the lies and made the statement that her M4 wouldn’t fire it’s 1st shot, it wouldn’t work due to the powder fine sand that had gotten into the rife. Not a shot fired in anger, when she needed it most. These rifles aren’t reliable or battle proven but one thing is for sure, the Adams Arms piston kit is both reliable and proven.
    Most of the desirable and expensive M4 or M16 are being made with some kind of piston system and they work, get the gun under water and come up firing, it works, do this with a DI gun and it will blow up. I’ve got an Adams Arms kit on one of my M4’s and am planning on putting these kits on my remaining 3 rifles. If nothing else it makes the gun much cooler and easier to clean than the DI system. That alone would be enough for me to ask why we don’t make our current battle rifles like this.

  14. BTW, US Special Forces including the SEALs use almost exclusively the H&K 416s with a 10.5″ barrel suppressed and H&K MP7s suppressed. However, Special Forces units can use whatever they want. I always carried what most of the other guys carried so kit was interchangeable. This was the H&K 416 and Sig Sauer P226 9mm pistol. However, I knew an old school Senior Chief that still carried a highly modified 1911 Combat Commander .45 cal. In my many years of experience with the AR I have found that DI and pistons have their pluses and minuses. I started converting or doing ground up AR builds with Adam’s Arms a few years ago (they are out of my home state and Jason is a jam up guy) and I couldn’t be happier. The advantage to me is a completely clean chamber and BCG. Literally, you just wipe it down. Also, if you run a suppressor, the weapon cycles so much better with an adjustable piston system (the reason SOCOM likes to run pistons). Either way you can’t go wrong. For anyone to say that the AR is “battle proven” because it has been in many wars and won is ridiculous though. Military issued bottom of the line Colts are POS. The US has won wars because of the people. I have personally known Marines that could kill someone using a banana as a knife! I’m an Air Force SF guy but the most terrifying and devistating piece of US military equipment is a 19 year old pissed off Marine!

  15. which is easier to clean and more reliable? my money is on the piston guns. having had and gotten rid of a very expensive rock river DI gun because it needed constant cleaning and specific ammo to be even sort of reliable and spent time in ak land with reliability but no accuracy, i have been very pleased to find that an inexpensive Olympic Arms rifle ($600) and the adams kit (got mine on sale $200) solved all my gripes. easy to clean and the bolt and reciever run so much cooler and no longer up to my elbows in solvent and sludge.

  16. Gas impingement guns are a sad problem in search of a solution. AK had it right, still does. crap where you eat = DI.

  17. Lots of back and forth here. Which one is better? Both systems have pros and cons, and those will vary from individual to individual. I say its the one that works best for YOU. Based on my almost 30 yrs of intimate experience with the AR platform, I lean towards DI overall. Standardized spare parts availability, ease of maintenance and reliable function in several different environments are some pros I see with DI. I have run a Ares piston retro kit on a 16″ and a 11.5″ (I like std. FSB guns, hence the Ares/FightLite kit) ran great until I added a suppressor using NATO ammo, which overgassed the unit causing piston malfunctions, they have since added a hard stop to their kits. Very little gas in the face with the Ares kit. Runs great with Wolf/Tula suppressed though. Adams Arms carbine kit has been a very nice system, easy to maintain and reliable, suppressed and non-suppressed, but maybe slightly more gas towards the face when running suppressed on a 12.5″ bbl. Inside of upper and chamber still get dirty, but only slightly less than DI suppressed. I would buy a Adams Arms for another 12.5″ build, using flip ups.

    Downside to any piston kit for the AR family is… non-standardized propriety parts. IF you need a replacement part, you are stuck with ONE company to acquire the parts from. As long as they are still in business and currently making that particular model, you might be ok.

    Im not sure why so many are concerned with the cleaning of a DI operated AR. Its not difficult nor all that time consuming to keep it running properly. I did a test several years back, with a DI carbine, using over 1,300 rds of Wolf, which is known to be way “dirtier” than LakeCity, with no cleaning, in several different environments, including a little rolling in sand, slow fire and multi-mag dumps, over several sessions, using old GI mags, with ZERO malfunctions whatsoever. When I did clean it, it still wasnt all that bad, less than running a suppressor for 3-4 mags. If cleaning or maintaining a AR in operational condition is too difficult or beyond your understanding(think outside the box), the AK might be for you. Here is a Quick clean tip, takes less than 2 minutes: Clean the chamber(not bore), just lube carrier(do not disassemble), wipe inside of upper(maybe).. then run it for another 500+ rds. The AR does NOT have to be polished spotless clean everytime to be reliable.

    To the old timers,(VietVets), please… enough with the jam-o-matic stories, the ARs, XMs and M16s you were issued 50 years ago are NOT the same ones of today, or even the the last 35 yrs.

    The DI AR platform isnt perfect, however it isnt bad either. Its a good, solid, reliable platform, that works as is. US is not the only military relying on DI operated ARs-M4s.

    Perhaps a dedicated FSB model from AA might not be too bad to have as a issued weapon….

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