Preview: Adams Arms AR-15 Piston Upper

Having done a few reviews in my time, I’m used to companies putting conditions on my ability to test their guns. “You can have it, but it needs to be back in three weeks.” “Use only brass ammo, and don’t feed it after midnight.” “Use only the provided lube.” And when I reached out to the guys at Adams Arms about testing out one of their piston-powered AR-15 rifles, they added a caveat of their own. But it wasn’t something I was expecting. Direct quote from the email:

Would you be willing to beat the crap out of our stuff and do your best to break it under real world application? If so were in.

I had never heard a firearms manufacturer say those words before and it was music to my ears. So, what’s the most adverse conditions possible for a rifle’s operating system? Short barreled rifle, suppressed, running the full gas setting, and using Tula ammunition. Now, 300 rounds later… Well, you’ll need to read the review for that. Stay tuned.


  1. avatar Andrew says:

    The more I look at AR’s the more bored I get. They’re just so.. dependable.

    In my mind they’ve become the 1997 Camry’s of firearms.

    1. avatar Hal says:

      Okay just watched the video. Is it just me or is he beginning to look like Farago?

      1. avatar Andrew says:

        i was actually thinking he resembled a Swarthy Young Tom Clancy!

        Aviators FTW!

        1. avatar Matt in FL says:

          Might want to check your definition of swarthy.

  2. avatar Hasdrubal says:

    Now if only they would finish the .308 piston kit I’ve been waiting for…

    Have one of their mid length kits and love it.

    1. avatar Bartman1 says:


    2. avatar frankgon4 says:

      I got tired of waiting for the .308 piston and I am off to pick up an FN FAL tomorrow.

  3. avatar ChainsawWieldingManiac says:

    I’m a happy user of an AA 5.45×39 piston upper. Had an issue with the piston breaking, but they replaced it under warranty pretty fast, with AA-paid shipping both ways. I’d probably recommend keeping a spare piston assembly around, but they’re only $50 or so… and it’s probably good advice for any AR piston system.

    As for a torture test, I’m thinking sand… I can see a lot of ways for it to gum up the works. Oh, and if you’re looking for stupid tricks, I hear you can run the AA piston without the spring on the piston.

    1. avatar bontai Joe says:

      I was thinking underwater, and maybe inverted underwater.

  4. Sandstorm? You have some ‘movie fans’?

  5. avatar BDub says:

    Did you ask them when they are getting around to making a 300 BLK version?

  6. avatar Jeh says:

    Piston…eh. Seems more like a gimmick then an actual improvement over the Direct Impingement.

    1. avatar Andrew says:

      You’re just looking to start a flame war, aren’t ya?


    2. avatar Rab says:

      Spoken like someone who has never used a piston AR

      1. avatar ensitue says:

        perhaps you could share with the rest of us why a piston drive beats a DI drive, especially when a suppressor is attached?

        1. avatar Mike says:

          If you only have a can on some of the time, you may get short-strokes due to a decrease in backpressure. A piston system allows you to turn the gas up or down by venting more or less at the gas block to counteract this.

      2. avatar Jeh says:

        I have not and I have no intention to. Having fired 8000+ through my AR
        (low #, but still no ammo thanks to SH) and having had only 2 jams, I see little reason to switch from a battle proven system, i.e. DI. Its really not that hard to clean, and its doesn’t require much.

        I say its a gimmick because the people iv spoken to give the same “its not that different, maybe kinda cleaner” response, and nobody seemed to care about it until HK gave some 416 to some SEAL’s.

        1. avatar Accur81 says:

          I have both DI and piston in my 5 AR’s ranging from 5.56, 6.8, and .50 Beowulf. I’d take the reliability of my Ruger SR-556 over my DI guns any day. It’s easier to clean a piston AR, and that even considering that one of my DI uppers has a stainless steel barrel with a nickel plated BCG and charging handle.

          Plenty of folks have called pistons gimmicks. They aren’t. LWRC and POF are top of the line ARs. The SR-556 is decent, although pretty heavy. There are a host of excellent DI uppers that typically have an edge over piston ARs in terms of accuracy and lighter weight.

          My gun safes have room for both.

        2. avatar Andrew says:


          How much cleaning of the bolt do you do on the piston rifle after firing at the range (say 200 rounds)?

          For me cleaning the bolt is really the biggest pain of the AR system. I know, first world problems.

        3. avatar Accur81 says:

          I’ve literally gone more than 1000 rounds without cleaning the SR-556. I was using a combination of M193, M855, and PMC .223. Wolf and Tula shoot pretty dirty, and I don’t consider them to be very reliable ammo.

          With that being said, the piston assembly got caked on pretty badly. I soaked the piston in Otis Ultrabore and scraped away for 10 minutes or so with a brass brush. It was good to go and cometely reliable again after reassembly. The only jam I’ve had was with Herter’s ammo on the #1 setting. Now, I just keep it on #2. I also don’t shoot a ton of Herter’s, Wolf or Tula.

  7. avatar Jeremy S says:

    I’ve been super happy with my AA 5.56 complete upper. Fit, finish, machining, bolt carrier, gas block, barrel quality are all top notch. 1:7 twist, chrome lined, CHF. It has been incredibly accurate, clean-running, and reliable for me.

    Testing out the Liberty Mystic on it for the first time:

    ^^^ it’s cool how you can easily turn the gas block to Off and the action stays totally locked up. Max quiet. No shell ejecting. No gas except out through the can.

  8. avatar Michael B. says:

    I have a mid-length Adams Arms piston upper and love it.

    It’s VERY similar to the FAL gas piston system and I love my FAL too!

  9. avatar Ralph says:

    using Tula ammunition

    Real men shoot Brown Bear. I mean, if you’re going to use crap ammo, use crap ammo not semi-crap ammo.

  10. avatar MikeH121 says:

    I run the Osprey Defense Piston. No springs no settings just load and go. It self adjusts to any ammo. Watch MAC freeze it up.

  11. avatar Todd S says:

    I’m glad that they believe in their product to the extent that they asked you to make it fail. They know you’ll give us the unvarnished truth about their product and if it’s shit, you’ll make no bones about it.

    1. avatar Matt in FL says:

      I hope their confidence is warranted. It’s cool to see things take a lickin’ and keep on tickin’.

  12. avatar cdphil says:

    I have a 11.5 for my sbr and I love being able to switch to half gas and run my 308 cyclone on my 5.56 ar…internals are cleaner and even after a few hundred rounds the piston dosent even get that dirty. And if i want i can turn the gas to off and run single shots

  13. avatar Accur81 says:

    Spoiler alert: Midway USA has these in stock. Average review is 5/5 for 15 reviewers. It seems mechanically quite similar to my CMMG M4 Lep II upper (mines a 6.8 Spec II), so probably runs like a champ and is accurate to boot. I guess we’ll see if it can maintain that level of satisfaction with crappy ammo and high round counts.

  14. avatar Scott says:


    Is this review coming soon?

  15. avatar az gunny says:

    I have a evo ultralight mid upper and noveske 2nd gen lower…all mil spec. By liitle bro has the same AA on a dpms basic comercial lower and littlest brother a bushy set up in DI. I’ve yet to have a jam 800 rounds of all sort including handloads accurate to 1 moa at 100yrds running burris ar-536 on by-pod and 2.5″ at 200 yrds. The DI…has A TON OF PROBLEMS IF IT FIRES. same accuracy. My mini 14 500 model doesn’t even operate as reliable as my AA. All that being said, you can have your DI! Everyone has their opinion, but if I’m going to battle…I’ll take my AA upper over most for the buck. And as far as warranty and parts. Their great and punctual!

  16. avatar Tim says:

    Piston for the AR is great if you don’t mind the loss of accuracy, carrier tilt issues, heavier, and a super hot hand grip due to the gas venting from that area.

    Also they have a much higher felt recoil to deal with.

    I’ll keep my DI ARs even when I’m running a can. It’s not worth the trade offs.

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