Piston System for AR 15 Questions and Answers

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Posted by Sic Semper Gumby on YouTube, this informative video titled “Adams Arms Piston AR 15 Strip Down: Show and Tell” (transcribed below) answers some common questions associated with a piston system for AR 15s. Learn about the piston kit broken down, carrier tilt, and how it handles 5.45 corrosive ammunition.



“Hey guys, so I’ve gotten a couple of questions about my Adams Arms 5.45 piston AR and I thought I would address a couple of those questions, and show you how it works with one broken down. As well as answer some of the other questions about how it handles corrosive ammunition. So first thing is first, I’ll go ahead and disassemble it. Ok, so this is the core of the gas system. So you have this little dial here, that’s fully open, that’s partially open sideways, and then if you want to actually close it all the way and not allow any gas to cycle, just put it like that. Now actually remove it looking at it like this you want to put it in the 9 o’clock position, click, and then this will pull straight out.


Now, the piston system is just a really simple two piece system very similar in operation to the VZ 58 surprisingly. Then, you have these little gas holes here which control how much gas is actually being directed into the piston itself which is more of a cup than anything it’s not a piston like you would think from an AK system. If we actually look here in the upper receiver, this spring here, slippery because of oil, is what keeps it pushed forward. The piston rod hits the bolt carrier group right there where you see that little circle. So instead of having a cup there to catch the gas like you would with a direct impingement system, you have this block here.


One concern I’ve read is you get something called carrier tilt where because of the force pushing it this way, your carrier will actually tilt like this when it is going into the buffer tube which can cause damage to your receiver or buffer tube. These are supposed to be carrier tilt proof, or designed to not tilt when their hit. Whether that is true or not remains to be seen. Aside from that, the bolt carrier group and bolt are pretty much a standard AR style bolt carrier and bolt. If you notice, this is spring loaded and that’s because there is a spring on the bolt itself. Standard firing pin, nothing special there. Standard Cam pin, again nothing special there. Then you have this spring right here which keeps your bolt in the forward position so you don’t have to rely on the cleanliness of the bolt and the bolt carrier to keep the bolt in the forward lock position. Now if you notice, the bolt itself has a kind of shade of gray and the reason for that is it is Melonite coated. From what I’ve read, Melonite is much more corrosive resistant than even chrome. The reason they did that is because they intended this rifle to be shooting surplus ammunition and 5.45 soviet ammunition.


If you take a look at the lower it is a Palmetto armory lower. I actually assembled this myself, put it together with a DPMS parts kit, Wolff extra-power hammer spring, and as I showed you guys before I have a buffer spacer and a carbine buffer spring and buffer in here. Now the thing with 5.45 AR 15’s is that you can’t use your standard 5.56 magazines with them, there is an exception to that, but ill touch on that later. If you look at this, this is a 5.45 specific magazine. The follower particularly is what makes it specific because the round is longer and because the rim is actually bigger than the cartridge case itself in terms of circumference. The follower has to tilt slightly upwards whereas with a 5.56 follower, it is more lateral. So because of that you won’t get 5.56 magazines to feed properly or even fully load up with a 5.45 the way you could with 5.56. Now the exception to that are the Magpul window magazines. Those could be unmodified and they will take 20 rounds of 5.45, and modified they can take 29 but you have to cut the follower. From what I’ve read they will feed 5.56 and 5.45 reliably if you modify the follower. That’s it for now. Just a short overview to show you my AR 15 and thanks for watching.”


Interested in your own piston system for Ar 15? Click Here to view the Adams Arms piston conversion kits available.

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