AR15 Direct Gas Impingement vs Piston Driven | Making The Switch to Gas Piston

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As gun enthusiasts, we’re always looking for new ways to improve and upgrade our AR-15 rifles and we have many choices when it comes to lowers, uppers and everything in between. In fact, so many choices that determining what is innovative and of good quality can be daunting. This is what I faced when I went to build my latest rifle. I was looking to build an AR-15 for under $1,000. I knew I wanted an Adams Arms gas piston operated upper. I was lucky to locate a 16-inch Mid Base Upper on sale.



Direct Gas vs. Gas Piston


A direct gas (or Direct Impingement System) utilizes the gases expended from a round fired to cycle the action of the rifle. The gases produced from the fired round travel through a gas tube back toward the bolt carrier. The increased pressure forces the bolt carrier to the rear of the upper, ejecting the expended round and reloading a new one as the bolt carrier returns. The expended gasses introduce heat and carbon into the receiver that eventually wear down the critical components of the rifle. This “carbonization” of the receiver causes the rifle to be prone to malfunction and misfire.


To eliminate this obvious weakness in the AR-15 design, Adams Arms invented the Retro-Fit Piston Drive System. Instead of introducing expended gases back through the rifle, their gas piston system utilizes a gas plug and drive rod sleeve to cycle the action of the rifle that never allows the gases to reach the receiver. With this innovative design, the interior of the AR-15 is exempt from heat and carbon build-up that direct gas systems experience.


Once I added the Adams Arms 16” Mid Base Upper to my latest rifle, I proceeded to test both systems with a hundred rounds each at my local shooting club. After returning from the range, I stripped both rifles down and it was clearly visible that the Adam Arms upper receiver was nearly free of carbon build up due to the fact that the contaminated gases never cycled back through the rifle. (See photo).


When cleaning the Adams Arms Retro-Fit Piston Drive system, you will truly understand the benefit of their elegant gas piston design; it’s simple and cuts the time it takes to clean due to the fact that you are not trying to remove carbonization from your bolt carrier assembly. Cleaning the Adams Arms Piston Drive system is simply brushing solvent through the drive sleeve and hitting the piston with a brush. I do this about ever third or forth trip to the range. This means more time to enjoy a cold one after a long day of target practice.


I have yet to experience a single misfire or jamming with my rifle since I’ve made the switch to the Adams Arms 16” Mid Base Upper. I’ve shot more than enough rounds through my rifle that I’m probably on some watch list for the Brady Campaign.


Ingenuity, reliability, and innovation are the best definitions for the Adams Arms Retro-Fit Piston Drive rifle systems. I now have the confidence that my rifle will be as reliable and efficient as the day I first bought it for many years to come. I highly recommend any Adams Arms upper assembly for your next AR-15 rifle. Their gas piston design rejuvenates the longevity of the AR model that will stand the test of time.


Nils Koenig

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