AR-15 Upgrades: Enhancing the Adams Arms Mid Base Piston Rifle

In a previous article, I reviewed the Adams Arms Mid Base, a midlength version of the company’s popular P1 carbine. Both feature a short-stroke piston system with a convenient and user-friendly gas adjustment. They come out of the box with some basic furniture and features, but are great hosts for some AR-15 upgrades that take them to the next level. 

A Little Background

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 round. The short stroke gas piston system rides under a midlength handguard. The flat-top receiver features the standard Picatinny rail for optics. There is also a small section on top of the gas block for mounting your front sight. Overall, the rifle feels solid, with no slop or rattle between the receivers and no grit when you’re working the action. 

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 standard, budget direct-impingement AR-15s. If you want to run your AR rifle hard and fast, but hate cleaning, you need a short stroke piston-operated rifle. 

Adams Arms rifle with Midwest handguard
A good M-Lok rail is a must for a tactical rifle.


With a few upgrades and some customization, you can take this base piston AR up a notch and make it an absolute tackdriver at the range. Plus, let’s be honest, it’s just too much fun not to upgrade your AR-15. I decided to start out with some basic AR-15 upgrades to help with the general operation of the firearm.

For me, a lefty, that means an ambidextrous safety selector and magazine release. I’ve adapted to using the standard components, but this makes things easier. It can also come in handy for right-handed shooters who may injure an arm. I selected a safety selector from CMMG and a mag release from Strike Industries — two companies with a good track record making AR parts. I also installed an extended charging handle from Radian, which makes manipulation much easier, especially with a magnified optic

While having some of these parts removed already, it was a good time to install a new trigger kit from RISE Armament. When installing a new AR-15 trigger, it’s easier to go with a drop-in trigger kit, because all the parts are contained in one unit that slides in and installs easily with two pins. The 3.5-pound RAVE 140, flat, match trigger was a perfect fit. This single-stage trigger features a crisp break and basically instant reset with no overtravel. This makes long-range accuracy a breeze when your fundamentals are in place. 

Moving forward, I knew I wanted a M-Lok rail for attaching accessories down the road. I landed on the Midwest M-Series two-piece handguard. It fits together easily and mates up pretty well with the receiver. Most importantly, it fits over the Adams Arms gas block, which can be an issue for some options. Further, it comes with a small M-Lok section for mounting a light, laser, or forward grip. I held off on those for now, since I’m planning to mainly use the rifle with a rest. 

Adams Arms Mid Base Rifle
Ambi controls are great to have even if you’re not left-handed.

Next, I turned to Magpul for a few classics for the stock and pistol grip. The ACS-L stock incorporates a small storage compartment for extra batteries or things. It provides a much more comfortable cheek weld and there is no loose rattle in the fitment. The MOE+ pistol grip has two hole slots for the mounting screw, allowing the shooter to choose between two different grip angles.

The rubber, shock-absorbing material feels exceptional in the hand. The extended beavertail gives you a great purchase. This swap could easily be done earlier while the grip is removed to install the safety selector. 

SIG Tango Optic

My favorite addition was the new SIG Sauer Tango MSR optic, a great, budget offering competing with the likes of Vortex. This 1-6×24 LPVO, or Low Power Variable Optic, is hard to beat, coming in around $399 with an excellent mount and removable lens caps included. As it came, it fit over the folding rear iron sight without modification. 

A note on the mount: A reference line is included for leveling the scope in the rings. This is a great time saver in the mounting process. The base is sturdy and secure, and utilizes captive mounting screws to secure it to a standard Picatinny rail. If you’re going to include a mount with your optic, it should be quality, so it’s nice to see that SIG didn’t cheap out here. 

SIG Tango Scope and Mount
The white line on the side helps you level your scope in the mounting rings.

This is a second focal plane scope, meaning the reticle is placed behind the magnified lenses, keeping it the same size at all magnification levels. Magnification is adjusted using a throw lever, which operates smoothly and fairly quickly. The lever features a knurled knob for easy access, but it is removable if you prefer to just use the raised, ridged section of tube. 

Additionally, the scope incorporates a diopter to adjust the clarity to your eye’s natural vision. The Tango offers generous eye relief, but the eye box is slightly limited and the scope has some tunneling at lower magnifications. Tunneling is when the field of view is wider than the limiting aperture.

Tunneling creates a black ring, tunnel effect when on lower magnification settings. This is acceptable for the price it comes in at. There’s always going to be some give and take. Overall, the SIG Tango MSR has great clarity and light transmission and provides a crisp picture. 

Windage and elevation knobs feature 0.5-MOA adjustments and protective caps to secure the turrets. These are not meant to be adjusted in the field, rather, the BDC reticle is set up for holdover points. With 11 brightness settings, finding your reticle is quick and easy in all environments and weather conditions. 

SIG Tango Reticle
Here you can see the SIG BDC6 reticle.

After some study, using the BDC6 reticle is fairly straightforward. Dot marks to the left and right of the center reticle represent hold points for leading a target. Hash marks under the center reticle display holds in 100 meter increments from 300–1,000. Further, dots spanning out from these hash marks indicate hold points for marking wind speeds at 5 and 10 mph. These marks are pretty hard to make out on the lowest magnification setting where you mainly rely on the illuminated dot, but quickly become clear as you zoom in. 

SIG Tango Specs

  • 1–6x Magnification
  • 24mm front objective, 30mm tube
  • Second focal plane
  • Reticle: Illuminated BDC6
  • Adjustment increments: 0.5 MOA
  • Low field of view at 100 yards: 124.8 feet
  • High field of view at 100 yards: 19.6 feet
  • Eye relief: 3.93″-3.74″ (low to high)
  • Diopter adjustment: +/- 2.5
  • 11 Illumination settings
  • IPX7 water resistance rating
  • Powered by CR2032 battery
  • Weight: 18.5 ounces
  • Matte black finish
Magpul ACS-L stock
Storage in the Magpul ACS-L stock is a useful addition.

How do the upgrades fare at range?

A common concern when you go changing out ‘what ain’t broke’ is whether it will continue to perform. Home built or modified ARs are known for having issues. That’s because you have a lot of people who think they snap together like Legos and don’t pay attention when installing parts. Some also like to cheap out on parts and order from unreliable, overseas sources.

If you purchase quality parts and install them with care, you should have success. Still, if you are not confident in your abilities, be sure to have a competent gunsmith look over your work if you’re doing anything major. You should also be sure to test your firearm to ensure it is functioning properly. Everyone makes a lemon eventually, and you want to ensure you don’t get a bad part. 

Fortunately, everything worked out in this case. No screws backed out and no springs snapped — everything operated as it should. Only time and use will tell, as even with a factory-built rifle, you could always theoretically be one round away from a parts breakage, but I feel confident in both the Adams Arms and the upgraded components. 

Target with .223 PMC ammo and holes
The Adams Arms performs well even with standard range ammo.

The Rise trigger was a huge aid to accuracy. A good trigger gives you less to think about on the range, allowing you to focus more on your shooting. I was able to consistently get 1 MOA groups or less out to 100 yards. I have not yet had a chance to extend past this, but it certainly seems promising. A trigger change is one area that can often cause reliability issues when done incorrectly. It was good to see that it hasn’t caused any malfunctions so far.

The upgraded safety selector and mag catch did not interfere with operation. Additionally, the stock, grip, and handguard completely changed the feel of the rifle. The gun balanced and handled much better for me now. 

Changing out parts is a good way to get to know your firearm and have a deeper understanding of its operation. Once you have swapped out some of your parts, your rifle will have more of a custom feel. This can be more fun at the range because you have a rifle that is uniquely your own. Certain upgrades can also improve your accuracy and handling, which will always put a smile on your face. 

Final Thoughts: Upgrading ARs

In a market flooded with competitively-priced direct impingement ARs, it’s nice to see another solid, piston offering come to the table — especially for the price. That gives you a lot of room for upgrades and customization, which is fun in and of itself. Take your time, select quality components, and build off a solid rifle and you’ll be ready to rock. 

What are some of your favorite AR-15 upgrades? What do you think of the improved Adams Arms Mid Base rifle? Share your thoughts in the Comment section.

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