In Review: Adams Arms 5.56mm MOE Carbine Piston Upper

During my time in the Army, I had dumped an unknown heap of green tips down range through various M4’s and M16’s. I can honestly say that I never experienced any real problems with the gas impingement system of the Stoner design. However, I quickly learned to dread the filth that would become of my BCG after even a short range session. I felt as though I was spending more time scrubbing carbon than flinging lead.

In subsequent years as a full-time civilian, I had pondered the idea of using a piston system, but never really liked the thought of retrofitting my rifle with makeshift parts. I wanted something that was designed and built as a piston system from the get-go. Unfortunately, this was a bit cost-prohibitive for a mere mortal, as the gas systems offered from Sig, HK and even Ruger were more than this ‘ol worker bee could afford.

The search for an affordable, accurate and robust short-stroke gas piston upper was what led me to a solution from Adams Arms. The Adams Arms 16″ Carbine MOE upper was just what I was looking for; simple, solid, light, accurate and affordable.

The Adams Arms upper provided a flawless fit on an Anderson Mfg. lower. There was virtually zero play between the upper and lower. I went with all Magpul furniture to match with the MOE fore-end. The result was a light and agile carbine that feels just about perfect for a general purpose defensive arm.

The gas block rail was fitted with a Magpul MBUS Pro all-steel sight as the plastic MBUS Gen2 is not recommended for this high heat area. The rear sight is a plastic MBUS Gen2. The sight combo works well for this set-up and still leaves room for a red-dot or holo-sight on the main rail.

ON THE RANGE

I tested the Adams Arms build using a combination of the following ammo types:

• Federal American Eagle 62g M855 5.56mm NATO
  • *Chrono’d this round at 2908 fps average at 29°F at 4400 ft. above sea level. The Melonite lining really works to speed things up* 
• PMC Bronze 55g .223 FMJ
• Silver Bear 62g .223 JSP

This was not a torture test. The initial test was of approx. 120 rounds total, and all shots were fired slowly. The carbine ate every round I put through without any malfunctions. It shot well with all three ammo types, with 50 yard groups ranging between 0.75″ and 0.95″. Being that none of these munitions were match-grade, I consider that very good. The POI was within 1 MOA between the various brands, meaning that with iron sights, you could switch ammo types without noticing much practical difference.

The gas piston system is simple and straightforward. It only requires a quick turn of the adjustment knob to remove the piston from the gas block.

The upper also includes a high-quality 1-piece Bolt Carrier Group [BCG] that helps minimize the issue of ‘carrier tilt’ that occurs in most systems.

The piston and rod assembly is easily removed for cleaning. Most of the carbon build up will occur where the two pieces join. This area is extremely easy to clean as it does not have nearly as many facets and nooks as the action.

I was pleasantly surprised after the range trip to find the action so clean. The bolt face had a little bit of carbon on it, but the rest of the BCG was almost spotless. An impingement system would be completely covered after 120 rounds. This one looked like it could eat 1000 before it really needed a cleaning.

There is also the heat factor; since the gases only go back as far as the front of the piston, the action stays much cooler. Also, the system can quickly be adjusted for normal, suppressed or manual fire, giving you extra options that are optimized for different applications.

I am very excited for the products offered by Adams Arms. They have a nice lineup and offer great value for your buck. For more info, see www.adamsarms.net.

Have fun and shoot clean!

UPDATE: 9/28/2017

After less than 700 rounds through the upper, I noticed significant wear on the inside of the upper receiver where the bolt cam pin contacts the receiver during cycling. Every time I shoot it, I find aluminum shards on and around the bolt cam pin where it’s upper edge removed chunks from the upper receiver interior.

Despite the excessive wear, it still fires and cycles perfectly. I’m certainly concerned that the receiver  is being permanently damaged as I have not see wear this rapid and significant on any of my other AR’s.

Multiple attempts were made to contact Adams Arms customer service via phone and email to inquire about this issue. Unfortunately, Adams Arms has been totally unresponsive to both email and phone inquiries. I am not sure how one would even be able to submit a warranty claim to them. As a result of the total absence of customer service and premature wear on their upper, I can no longer recommend Adams Arms to our readers. It is unfortunate, as we really liked the product initially.