Adams Arms Piston Review

Murdoc has written a review of the Adam Arms retrofit piston system for the AR-15 for Guns and Hunting.

The new Adams Arms gas block quickly mounted with hex screws and a new bolt carrier key, a couple springs and a bushing were all that was needed before adding the sleeved drive rod. Supplied front handguards mounted normally, and I was left going back over the installation manual, convinced that I must have missed something. It was that easy. Though it took me more than half an hour due to the troublesome factory gas block, this is certainly a task that can be accomplished by a moderately capable gun owner.

It is a well written review and worth reading.

This 3D animation shows how the piston system works verses the AR-15’s normal method of operation, direct gas impingement.

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.


  • Valhalla

    so, does this increase its maximum semi-automatic firing abilities, or just keep the gun cleaner?

  • Tom

    I’ve got three piston kits on my list of candidates for my next build, and Adams is up there. My only real worry is whether or not it’ll fit under Yankee Hill free float handguards, which I’m rather fond of. My current rifle has a “smooth carbine” handguard, so if the kits by CMMG or Adams will fit under that I’ll be saving up for one!

  • Ken

    Interesting…How do you prevent blowby on that “cone shaped” piston. Just a nerd question…lol!

  • Dom

    This is one of the reasons Mini-14 owners like Mini-14s. If only Bill had built an accurate gun, it would have been great. Adding this to your AR is very, very cool.

    Not sure about ROF but it definitely keeps the mechanism cleaner and thus more reliable. Blow-by definitely happens, Ken, I can tell you from experience with my Mini, but it doesn’t hurt anything.

  • Carl

    While the piston looks better in theory, I understand there are some subtle advantages of the direct impingement system, like the recoil force being more on the center of the bore, and perhaps the barrel being subjected to bending forces from the piston. Or something else nobody has thought of…

    As always when upgrading or changing something, rigorous training and testing in the environment you intend to use your tool is prudent.

  • Tom

    @Dom: Except the Mini-14 doesn’t use a gas piston 🙂

    While the operating rod design of the Mini-14 is in some ways similar to a piston system, it’s actually got more in common with Remington gas-operated shotguns than true gas piston guns like the FAL or .30 Carbine. For anyone not familiar with the Mini-14 or piston systems, I’ll go into a bit more detail…

    Whereas a piston setup like the Carbine vents gas to push the piston into the op-rod assembly, the force of which pushes the rod backwards and operates the bolt, the Mini-14 has a gas aperture or valve which directly vents gas into a cavity on the op-rod. I guess you could say the Mini-14/Remington design eliminates the middle man, but it still cruds up the inside of your stock! The crud just isn’t in the working parts of the action, which is the big argument against direct impingement.

  • jake

    Why would you want to do this to a gun? like, what are the advantages?

  • jdun1911

    Valhalla, AR15 piston does not make it cleaner nor more reliable. However, it does make it easy to clean.

  • splatacaster

    How much would you have to shoot to notice a need for having either a long or a short stroke piston operating system??????
    Which is the best way to go long stroke or short stroke??

  • glwbear

    I have a ADAMS ARMS Piston system in a AR Pistol and after some minor adjustments it is a super system to have!

    It makes the Gun so much eaiser to Clean and NO more carbon build up in the Bolt!

    I highly recommend it.

    34 years Law Enforcement & the Private Sector

  • Bobby

    Why does everybody not want to clean their rifles?

    I want the piston system because it’s more reliable.

    That’s why I use the M6A3.

  • I just installed the darbine length system with one piece bolt carrier about a month ago on a custom upper with a Daniel Defense 9.5 FSP Light rail. I have 2 other uppers one a 16 inch barrel with a AK 74 muzzel brake and the other a 20 inch with a rifle length gas system and both are Direct Impengment. After compairing all uppers the Adams Arms piston retrofit does make the rifle run cleaner and cooler where it counts, the bolt assembly! The recoil isn’t much different than a DI system but then the two DI uppers I have are Bull Barrels and one is compensated so they don’t move much. The AA Piston upper is lowder than the others due to a shorter barrel length and I’m using a FSC 556 Bulldog Brake from Addax Tactical (designed by Primary Weapons Systems) but all of that asside if feel like I’m shooting my Ruger 10/22!
    I don’t have much expierence with many other Piston uppers other than POF which is very well made as well so my recomendation is buy an Adams Arms kit.

  • kershaw t

    will the adams kit work on my M @ P ar15 ?

    • zak

      Yea, Just take off the upper, attach the 5.45 upper to your S&W lower, and put in the 5.45 mag.

  • skoal

    I bought the Adams Arms piston Kit 2 weeks ago, and it just works! There is no carbon in the bolt or bolt carrier. Just use your common sense, where do you want all the junk, in the front or in action, that lets the job get done?
    I’m 58yrs. old been to nam and see what the di system does, just get over it, and try something new…..and this does work, I’m totally amazed.
    Common sense will tell anyone, if you are going to put the carbon back in the action, the action slows, just think about it, and you will see! And to all the guys and gals that want to use the di system go ahead, but Adams Arms system works, and that’ the long and short of it. If you don’t like it, don’t post, unless you have tried it, and I have and it works!!!

  • Robert

    Dunhams in Pa stores have the new American Tactical AT-15 with the new Adams Piston system for $699 on sale normaly $799.

    Anyone know how dependable this system is or how it has been working?

  • I have a pistol length gas piston with the bolt on gas key,I installed exactly what adams arms instructed me to do.After 25 rounds the piston rod broke into two piece.Eventually the rod pushed the solid gas key up jamming my Bgc and got stuck,it was a pain to disassembled it.You need to buy their one piece carrier and stay away from the gas key bolt on.Other than that it was flawless!!

  • Mike

    The Adams kit shown here is GREAT! But it’s actualy more like the Mini 14 gas system than a true piston system, like the M14 or the new Ruger SR556. I have the Adams kit on an LRB upper. Works awesome. 0 problems and runs as clean as an AR can. Anyway the “piston” in this kit doesn’t move. It’s more or less a “pipe” that the gas goes through, then it expands in a small gas chamber that is part of the transfer rod which gets pushed back thus cycling the bolt. Just like on the Mini 14 gas system. There’s obviously a big difference in the way the parts between the two systems look, but the actual physics are the same. So the gas chamber moves, and the gas “piston” is stationary. The total oppisite of traditional (M14) piston systems where the piston moves inside of a stationary gas chamber and hits a transfer rod to cycle the bolt. I actually like the Adams kit more than a traditional piston system. It’s simple and easier to clean in my experience. That’s why I chose it. And I’m glad I did.

  • L J Gates

    You need to know that Adams early pistion systems come with an engineering defect.
    The gas plug has a e-clip that will fail and render your system in-operable.
    Their customer service dept. says they will replace it with a re-engineered gas plug.
    So far I have found their Cust. ser. to be slow in responding
    Buy with caution

  • Randy

    I recently had my gunsmith built me a new AR15. The gunsmith alone was great but the real surprise came from the precision craftsmanship of the upper we went with on the build. I am one that likes to keep my money in the area I live. So we decided to go with a Adams Arms Piston upper. After many range trips and a ton of ammo later. I can honestly say it was the best decision I have ever made. This is not my first AR15 but in my opinion it is the best AR I have ever owned. The Adams Arms upper and piston system has worked flawlessly under very heavy use. Cleaning the gun now is a quick and easy task due to the design of the their system and the coatings they use. I could not be happier with Adams Arms and the customer service I have received from them. I highly recommend this company if you are looking for a no hassle, quality built AR upper.