I’ve often wished that I’d been born in the post World War II era of the 50s and 60s. The technological boom is something that I would’ve loved to experience. History, unfortunately, is rarely noticed at the time it happens. It normally takes decades for something’s worth to be recognized. But there are those occasional quiet wonders that get noticed and become “lighting in a bottle.” I felt one of these historic moments as I walked past a manufacturer’s table at a firearms industry show in late 2008. The manufacturer was Adams Arms.
There sitting on a table was something that I instantly knew would change it all. It was the new Adams Arms piston-driven Personal Defense Weapon (PDW) with a 7.5-inch barrel. That’s correct—I did say a piston system for an ultra shorty. I stared for a moment to be sure that I was seeing things correctly, then asked Jason Adams, “You’ve got a piston system for a seven and a half?” Jason smiled, “Yes, we do, and it works flawlessly.” He then started right into an expository tutorial on the system that bears his name. For those who aren’t aware of what piston systems are, allow me to educate you.
Time + Temperature + Pressure = Gas. I’m not talking about Super Bowl Sunday here; I’m talking about AR-15s. It’s gas pressure that makes ARs work. Whether it be Direct Impingement (DI) or Piston Systems, ARs are at the mercy of gas. Aren’t we all?
Adams Arms has mastered the science of AR gas operating systems and made it available to the masses in their AR15FIX Kit. While some would grouse that $499 (the current cost of the Adams Arms Kit) is too much to spend on a piston system, consider this. If you buy a dedicated piston gun you’ll be paying close to a couple grand for the thing. Even if you just buy the upper you’ll still be at the roughly $1000 mark. Why not just keep the gun that you already like and retrofit it for only $499? Problem solved.
The Adams Arms piston is a breeze to install and consists of the following: Gas Block, Adjustable Gas Plug, a one-piece Sleeve/Drive Rod assembly, Bolt Carrier Key, and Drive Rod Spring. If you can knock out pins with a hammer and turn a wrench, you can do this. The system is fairly straightforward and failsafe, for that matter. Much has been written about this piston system and the Adams Arms home page offers links to several of these articles.
If you haven’t heard about Adams Arms by now you’ve been living in a hole—shame on you! What I really want to do with this article is focus in on why this particular system is the one that can take a problematic, temperamental little beast like the 7.5-inch PDW and transform it into a “bet your life on it” piece of rock solid gear. Primarily it’s the fact that Adams Arms isn’t really using a “piston” per se. The term piston is used loosely here to describe a non-DI gas-driven gun. It’s the Adams Arms system that really stands out above all others due to its ingenuity. For starters, the Drive Rod has been simplified as a one-piece assembly instead of multiple, and the piston isn’t really just a “piston.” It’s a piston inside of a cylinder. You can also remove the entire system through the front of the gas block for periodic cleaning, and showing off. Trust me, you’ll do it; people will ask to see it if you don’t.
Imagine the durability and reliability of an AK-47, and the accuracy and finesse of an M16 all rolled into one ultra-short, highly maneuverable gun. What you get is the Adams Arms PDW. The piston system is not really all that new of an idea. However, what Adams Arms has done with this already well established idea is to perfect it for the AR platform, and hone it into a reliable system that’s ready for the 21st century battlefield. Go ahead, abuse it, it’ll simply ignore your torture and keep cycling round after round. By the way, this is the only system where you can dial your gas-flow rate up or down to include even completely shutting the system off. This means that when subsonic/suppressed operation is needed, your bolt cycling won’t give you away.
As I began to work with this system about a month ago I received an email from Adams Arms VP Jim Granger. He said that he had a surprise for me and was sending me their new one-piece Bolt Carrier Group (BCG). When I first opened the box I fell silent. There in precision-engineered steel was a chromed, laser-engraved masterpiece. The new BCG is that one piece that we’ve all been waiting for, and here it is.
The one malfunction that takes all piston guns out of the fight is the occasional broken strike key/gas key adapter. Whatever you wish to call it, it’s that piece that replaces the standard gas key on the BCG of direct impingement ARs of old. During an informative conversation with Jim he explained something to me that qualified a lot of rumors that I’d been hearing about piston systems. If the system isn’t installed correctly or the specs on your gun are off, your strike key will start experiencing a “hit” instead of a direct contact impulse from the rod assembly. If your AR isn’t set up correctly and the rod assembly isn’t making contact with your strike key it’ll get hit by an unimpeded, accelerating rod over and over until it shears off.
To eliminate this problem Adams Arms makes things as simple as possible with their drop-in AR15 Fix Kit. They’ve also addressed the weak points in the BCG by machining a strike mound into its contours, thus creating their first-ever one-piece BCG. Not only does this one-piece BCG create a much stronger system, it also does away with the margins of error that existed in a bolt-on strike key. The bolt is also assisted in its duties by a spring that actually installs behind it inside the BCG. This spring, while tiny in size is a giant in function. The only other manufacturer to use this spring-assisted BCG is Heckler & Koch, however HK can’t dial their system up or down like Adams Arms can.
The Adams Arms one-piece, spring-loaded BCG now comes as a drop-in part that’ll fit and fix all existing piston systems on the market. What this seemingly innocuous little spring does is to retard the disconnect time long enough to reduce backpressure in the system. It also helps your bolt disengage from the barrel extension cleanly instead of being ripped out by the sudden rearward travel of the BCG as it’s pushed by the rod assembly. In essence the spring mimics the more smoothly running gas systems of old without all the fouling that gets shot back into the upper. The one-piece BCG system also eliminates cam pin drag. The spring makes the mating surfaces between the carrier, bolt, and cam pin float smoothly past each other. The bolt is so well balanced with the spring inserted that if you take it and place it bolt down on a tabletop, it’ll actually support the entire weight of the carrier above it but will flex downward at the slightest push. It also makes inserting it into your upper an easier task all around. No longer do you have to swing the BCG out to get the bolt to lock in an extended position; it’s always that way from the positive pressure of the spring.
Another eye-catching feature of the new single piece BCG is its uniquely flared-out tale sections. They’re referred to as “skis.” They’re machined into its base and keep it from torquing about inside your upper and buffer tube while in cycle. This ensures less unintended movement of your BCG when it’s traveling back and forth, thus reducing wear on your upper and buffer tube. Lastly, the chrome finish on the BCG makes those few bits of fouling that actually happen to make it into your upper fall away like so much dust. After a rather lengthy shooting session during testing I found that the BCG could be cleaned by simply rubbing it with my finger tips to loosen the small amount of fouling on the bolt and then just wiping it clean with a rag.
Short Barrel Fix
I like SBRs immensely; they’re a fix to a big problem—maneuverability. While the 10.5-inch SBR is about as perfect a balance as you can get in CQB operations, it lacks greatly when you’re talking about fighting from inside of structures. This is where the PDW platform really comes into its own. The problem of fouling and failure is inherent in a 7.5-inch SBR. Due to their short barrels they’re notoriously temperamental when it comes to consistency with different types of ammo.
An SBR will still be in the process of burning propellant when it begins to unlock its own chamber. SBRs tend to run a bit faster and will inject a gout of liquid fire into the upper and increase your chances of failure caused by excessive fouling. Most engagements usually only last seconds and will probably cover a magazine worth of rounds at best. The problem isn’t so much in the short run but in the long run.
Even after just a few rounds are fired through a shorty it starts to look like the lasagna from Hell on the inside and around the ejection port. You know that caramelized goo that you find around the rim of a lasagna pan? That’s the same stuff you’ll find inside of an SBR that runs on a DI gas system. What happens is that all the unburned powder takes on a liquid type effect and blows onto everything. As it cools, it sticks like glue and fouls your weapon. Over time, this gets harder and harder to clean off. Every time that you fail to apply elbow grease to clean your SBR, the fouling becomes a little more permanent. Eventually it builds to the point that your gun starts failing and you end with a gun blowing up in your hands.
Adams Arms has truly filled a market niche with their initial piston systems that cover everything from 22-inch guns all the way down to 10.5-inch guns. However it’s the evolution of their 7.5-inch system that really has started turning heads.
A while back my friend and custom armorer, Shawn Temple, of Tennessee Police Supply, mentioned that he wished that I’d shown some accuracy shots of a 7.5-inch SBR that he helped me with on a previous article. Well now is as good a time as any, and with the Adams Arms system on board I can’t think of a better gun to do it with.
I started shooting up close for speed drills and found that the Adams Arms system did a nice job of keeping the weapon clean and cool. However, I discovered a nice surprise that I failed to mention earlier. The Adams Arms system actually blows all the fouling and excess gasses away from the operator. The only real sign of fouling that you find is a patina of crimson along the front of your handguard from where the system vents out. This, incidentally, cleans off very easily.
I found that when I stepped to the 25-yard line the groupings were still inside of 2 inches. The piston system seems to cycle the weapon straight back into your shoulder and the recoil is smooth and manageable. Also, with such a short barrel the question of penetration arises. I can assure you that this PDW can punch holes right through Level III-A body armor, as evidenced by the vest that I defeated with four well-placed shots. Remember that bad guys wear Kevlar too.
Suddenly pistol-length SBRs are a real option when it comes to making a choice for law enforcement, military, dignitary protection, and so on. No longer can the excuse be made that a longer barrel is preferable because it…blah, blah, blah. With the Adams Arms AR15Fix Kit there is no gun that can’t be made to run flawlessly and accurately. Imagine having to reach for your SBR in a bind. As the enemy’s rounds snap past your head you hit the dirt. Debris goes everywhere, but you know that your gun is going to work because your Adams Arms Kit was designed with this kind of moment in mind.
There is no longer an excuse for failure of an AR platform. Adams Arms has proven that big solutions can indeed come in small boxes.
I’ve often wished that I’d been born in the post World War II era…
by Abner Miranda / May 9, 2009