Review: Adams Arms Mid Base Piston AR-15

Adams Arms on fence

We see a lot of ARs, a lot. Most are decently accurate, reliable, and durable. Standard direct impingement guns with one upgrade or another are common. It is a simpler system that’s easier to get right. Expensive, $1,000+ rifles are also popular. So, it is exciting and refreshing to see something different come to the table. The Adams Arms Mid Base features a short-stroke piston system with a convenient and user-friendly gas adjustment. It is the midlength version of the company’s popular P1 carbine. Both are practically identical in other features.

Piston ARs are nothing new, but they can be pricey. The Adams Arms design works well and comes in at a price point that provides an excellent alternative to the standard budget D.I. AR-15. If you want to run your AR rifle hard and fast, but hate cleaning the bolt, you need a short stroke piston-operated rifle.

Adams Arms on brick
The Adams Arms Mid Base is ready for use.

Adams Arms Features

The Adams Arms Mid Base rifle features a 16-inch barrel, with a 1:7 twist rate and is chambered for the 5.56 NATO. The short stroke gas piston system rides under a midlength M4-style handguard. As it comes, it’s very thick in order to house the gas system, but it works well. Additionally, the rifle incorporates a standard 6-position collapsible stock, as well as an A2 pistol grip and flash hider. Let’s be honest, you’ll want to upgrade and customize those for yourself anyway. This keeps the initial cost down. 

The flat-top receiver features the standard Picatinny rail for optics, but there is a small section on top of the gas block as well for mounting your front sight. Overall, the rifle feels solid. There is no slop or rattle between the receivers, no grit when you’re working the action, and the safety clicks nicely into place. The standard G.I. trigger pulls at around 6–7 pounds. This is one area that could use an upgrade, especially if you want to stretch out to further distances

Because of the piston gas system, there’s no gas key on the bolt carrier. Instead, it is one solid piece and full-auto rated. This is a more durable design, as this is a point that can shear off under repeated hard use. 


  • Caliber: 5.56x45mm NATO (accepts .223 Rem.)
  • Barrel: 16-inch, 4150 steel M4 contour with 1:7 twist
  • Finish: QPQ Melonite/Black Nitride
  • Overall Length: 32.5 inches (collapsed)
  • Weight: 6.2 pounds
  • A2 flash hider, 1/2″-28 thread
  • M4 feed ramps
  • Short stroke, piston-operated, midlength gas system
  • Picatinny railed 0.750-inch gas block with 3 adjustment settings
  • Full-auto rated bolt carrier with integral piston strike face
  • Flat top, optics-ready upper receiver 
Adams Arms gas system
Here you can see the gas system separated out.

Adjustable Gas System

The hallmark of the Adams Arms rifle is the adjustable gas system. Under the front sight post, the gas block features an adjustment knob. Simply depress the spring-loaded button and turn the knob. When facing the muzzle end of the rifle, turning the knob clockwise once will cut the gas to 50%. Two turns will eliminate the gas and essentially make the gun single shot. Turning the knob counterclockwise will unlock the gas system for removal.

Once unlocked, it simply slides out for easy cleaning and maintenance. When the knob locks into position, you will hear the spring-loaded button click back into place. The standard 100% gas setting has the button facing up at 12 o’clock. 

The version reviewed has three gas settings: 100%, 50%, and 0% for standard, suppressed, and single-shot fire respectively. Adams Arms also offers an upgraded version for those who really want to dial in the gas system to their specific rifle and ammunition load. It incorporates 5 percentage options (100, 74, 53, 32, 11) and an optional low-profile gas block option. This is nice, but not necessary. I’m assuming this is mainly to allow the use of standard free-float handguards of the shooter’s choice. Currently, you are limited to what will work around the larger gas system setup. 

Pink torso target
The Adams Arms Mid Base averaged 1-inch groups at 25 yards.

Range Testing

So, how did this gas system fair at the range? Simply put, it ran great. I had no malfunctions in the 100 rounds I fired. This is a limited sample, and we’ll see how it does in further testing. However, it hasn’t hiccuped so far. I even tested the single-shot, no-gas mode. To no surprise, it functioned as intended. You must manually cycle the rifle after each round fired.

I did not have a suppressor on hand, but I hope to test out the 50% gas function in the future and will provide an update. I fired a mix of PMC and Armscor 62-grain brass target ammo in Magpul PMAGs. This is optimal bullet weight for the 1:7 twist barrel. 

It tested the Mid Base rifle with a UTG Accu-Sync red dot optic. This is a great lightweight optic with no magnification and a 3 MOA dot. After an easy sight-in, things were up and running. I fired both rested and standing to ensure nothing interfered with the gas system and reliable cycling.

Adams Arms gas block
Here you can see the adjustable gas block and push button.

My supported groups averaged around 1-inch at 25 yards. I’m still working on my rifle shooting, but this is better than my groups in the past. I’m sure the Adams Arms can make even a novice shooter look decent. We’ll see how it continues to shoot, stretching farther out in future testing. 

Final Thoughts

In a world of competitively-priced direct impingement ARs, it’s nice to see another solid piston offering come to the table, especially for the price. For well under $1,000, you’re getting one helluva rifle that is done well, with great gas adjustment features. That leaves you a lot of room to upgrade and tailor the rifle to your needs. I’m excited to keep working with the Adams Arms Mid Base and look at some upgrades to take it to the next level. 

Do you prefer a D.I. or piston AR-15? What do you think of the Adams Arms Mid Base? Share your thoughts in the Comment section.

  • Adams Arms and UTG Ascu-Sync
  • Adams Arms gas system
  • Adams Arms gas system
  • Adams Arms rifle gas block
  • Adams Arms gas block
  • Adams Arms P1
  • Adams Arms on fence
  • Adams Arms on fence
  • Adams Arms on brick
  • Pink torso target

About the Author:

Alex Cole

Alex is a younger firearms enthusiast who’s been shooting since he was a kid. He loves consuming all information related to guns and is constantly trying to enhance his knowledge, understanding, and use of firearms. Not a day goes by where he doesn’t do something firearms-related and he tries to visit the range at least a couple of times a month to maintain and improve his shooting skills.

His primary focus is on handguns, but he loves all types of firearms. He enjoys disassembling and reassembling firearms to see how they work and installs most of the upgrades to his firearms himself, taking it as a chance to learn. He’s not only interested in modern handguns and rifles, he appreciates the classics for both historical value and real-world use.
The Mission of Cheaper Than Dirt!'s blog, The Shooter's Log, is to provide information—not opinions—to our customers and the shooting community. We want you, our readers, to be able to make informed decisions. The information provided here does not represent the views of Cheaper Than Dirt!

Comments (10)

  1. @ROCKIT… (and I gotta ask, is the name a Herbie Hancock reference 😆) yeah, probably so. Ambi controls on an AR style really wouldn’t cost the mfgs. much of anything, really. Not like they’d be losing money if they did it and not charge extra. For me it’s not really an issue because I prefer to shoot right handed but it’s painful to watch Pop try and shoot my AR… he looks super awkward with it. That’s why I got him a Mod 94 and a Mossberg 500 years ago… easy for left handed shooters to operate. As far as Buzz Light… it should’ve been boycotted a LONG time ago. It’s overpriced water. At least we have Yuengling… and Killian’s. 👍🏻 Maybe we can get Buzz Light to finally go away. Ambi golf clubs… hmm… I’m a pretty smart guy and would like to see that, no way I could come up with something… I have no clue how that would even begin to work because of the face angle of the heads. Someone would certainly become a millionaire several times over if they could make that work though. And I can’t remember who now but there IS a straight up left handed AR style carbine/rifle made by some reputable maker… I know there are left hand upper recievers out there.

  2. @SGT. DAVIS – Looks like your family is the perfect example of why AR manufactures should include Ambidextrous Controls, which actually only cost a few pennies more if that is all they made. I am sure some entrepreneur could figure out a way to make golf clubs ambidextrous too. Thank you for supporting my BudLight stand. 😉

  3. Don’t drink Buzz-Light anyway so the boycott is pointless to me… Yuengling is great but only have it on rare occasions because of cost… now on to the rifle. Yeah, left eye dominate is a thing, Pop is and shoots left handed. Forget trying to set anything up for him. I’m left handed (ambidextrous actually) but right eye dominate. I can shoot either way but use right eye with both eyes open. Otherwise I don’t do well. Strange, I know. I play drums and guitar right handed, shoot basketball right handed, but golf left handed, baseball… bat and throw both. 🤷🏼‍♂️. As far as piston driven ARs, yeah they’re cool and all but the biggest issue I’ve always had with them is they all seem to be propritary systems… unlike the DI systems which pretty much all interchange. My BIL has a Ruger piston driven AR… it’s a champ but if anything goes wrong with it it’s Ruger parts or nothing. Speaking of left vs right… BIL is left handed but golfs right handed, shoots right handed, shoots basketball left handed, bats and throws left handed. My son is left handed but shoots right handed, bats and throws left… my nephew is right handed but shoots left handed. Yup, we’re a bunch of oddballs here. Not in the market for another AR but that one doesn’t look too bad though… if I actually cared to have a piston driven AR.

  4. @GUN GEAR MAN, it is believed to be more like 30+%, which makes it well worth going after that market, and yes, I do know how to install ambidextrous controls, but in todays tactical training environment, it isn’t necessarily about being Left-eye or Right-eye dominant, because tactical training now expects, and requires, to switch hands. I don’t know where you buy your stuff, but your prices seem a little high. Like many things today people are tired of, I am tired of a new AR, that doesn’t consider the needs of Left-eye dominant people. In other words; It is my “Bud-Light” stand, so if they want my business, they will be expected to go the extra mile. If Left-eye dominant people do not take a stand, then you can keep pretending it is fine to use a Right-hand only rifle. Me, I will go with Yuengling, which also cost twice as much a Bud-Light now. LOL

  5. Did I miss it or was there no price listed for this weapon? It looks interesting but curious as to the cost

  6. Rockit- This is an entry level piston AR. Good grief man. The Sig piston MCX is $2700, the LWRC is $2600, and RedX Arms doesn’t offer a piston. All that angst because you don’t know how to install a $40 ambi safety? I’m a lefty too, and usually just add a ambi safety and maybe a charging handle.

    What’s the ratio of left to right eyed dominant shooters 10% to 90%? Adding that cost to the 90% that don’t need ambi controls doesn’t make good business sense.

    I think it’s time for you to switch to decaf.

  7. “Piston ARs are nothing new, but they can be pricey.” Yet still too cheap to include Ambidextrous controls. At any price, if an AR doesn’t INCLUDE Ambidextrous controls, it will NEVER be on my bucket list, as they obviously are not interested in attracting the business of those of us who are born Left-eye dominant. That is fine, because there are other options out there. Hello Sig, Hello LWRC, Hello RedX Arms.

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