{"id":419262,"date":"2024-04-15T13:00:11","date_gmt":"2024-04-15T18:00:11","guid":{"rendered":"https:\/\/gunmagwarehouse.com\/blog\/?p=419262"},"modified":"2026-01-13T14:14:08","modified_gmt":"2026-01-13T20:14:08","slug":"ak-47-upgrades-why-add-an-adjustable-gas-piston-to-an-ak-47","status":"publish","type":"post","link":"https:\/\/gunmagwarehouse.com\/blog\/ak-47-upgrades-why-add-an-adjustable-gas-piston-to-an-ak-47\/","title":{"rendered":"AK-47 Upgrades: Why Add an Adjustable Gas Piston to an AK-47?"},"content":{"rendered":"

When I began this project, overhauling a stock WASR Romanian 7.62 x 39 AK<\/a>, I really wanted to address the externals. AKs have always fascinated me, and I wanted to take one through a solid revision and see how some modernization impacted the performance. Now, on my third pass, I\u2019m diving deep inside and working on the piston.<\/p>\n

What\u2019s wrong with the traditional AK piston?<\/h2>\n

I\u2019d take an AK\u2019s piston over a direct impingement AR any day, personally, but there are still some issues with the AK-47\u2019s piston if you want to shoot suppressed. The main one is the lack of adjustability. If you intend to shoot suppressed, an adjustable piston will allow you to dial in the gas pressure to keep the pressure balanced.<\/p>\n

When an AK (or any gas-operated rifle) fires, the bullet travels toward the end of the barrel. Behind it, pushing the projectile is a burning cloud of gasses. In the split second before the bullet exits the barrel, some of that gas is diverted into the gas tube, where it pushes a piston back toward the shooter.<\/p>\n

This is the action that drives the bolt to the rear, ejects the empty brass, and compresses the spring that\u2014when the pressure subsides\u2014drives the bolt back into battery. It is a beautiful thing to watch in slow motion.<\/p>\n

\"This
This Century WASR AK in 7.62 x 39 has been through a lot of changes recently. Much of what can be replaced has been swapped out. The goal is simple–take a reasonably priced, stock AK and make it run like it should.<\/figcaption><\/figure>\n

What happens when you add a suppressor to an AK?<\/h2>\n

The goal, obviously, is a serious reduction in the noise of the 7.62×39 report. The suppressor will capture the expanding gasses, redirect the path of those gasses, cool them dramatically by forcing them in, under, and around a lot of internal surfaces, and still allow the bullet to escape unimpeded.<\/p>\n

But the suppressor interrupts the natural path of the gas and creates back pressure in the system. Too much gas. That gas wants to escape however it can, and some of it presses hard against the piston.<\/p>\n

When there\u2019s too much gas hitting the piston, it may travel faster than it should. The repetitive stress of a gun that\u2019s over-gassed adds wear to the action. It can even break parts. Actual breakage is uncommon in the AK platform, but there\u2019s still no reason to beat your gun up.<\/p>\n

The AR platform addresses this problem most commonly with an adjustable gas block. These exist for the AK, too. The adjustable piston, though, is also a solid option. Make sure you get the right gas length\u2014like this one for the AKM<\/a>.<\/p>\n

\"A
A mess of AK-47 upgrades in progress, including a new trigger and a new safety.<\/figcaption><\/figure>\n

The KNS Precision Adjustable Gas Piston<\/h2>\n

The way this works\u2014once it is in the gun\u2014is easy to understand. The collar has grooves running perpendicular to the piston\u2019s shaft. Gas, hitting the plunger, escapes down these grooves. Turning this collar moves it up or down, restricting or opening up the line for more gas.<\/p>\n

As all of this is enclosed within the gas tube, you will need to open the gun up to make adjustments. After installation, take the gun for a test run.<\/p>\n

Before you start on the build, take the gun (assuming you\u2019re not building this from the ground up) and have an assistant shoot some video of the action moving during live fire. You may be attuned to how the rifle runs in its stock form and know how it feels.<\/p>\n

After reassembling the gun, you\u2019ll repeat this. Close off the piston\u2019s vents and then do another test run. In this configuration, without a suppressor, everything should be running as it did before. If it isn\u2019t, the video will show, and you can make adjustments accordingly.<\/p>\n

With a suppressor attached\u2014that\u2019s another topic entirely\u2014you\u2019ll want to do another test-fire. This is a trial-and-error sort of thing. I tend to open the system up completely\u2014taking the piston from the most closed off to the most wide open\u2014for these tests.<\/p>\n

The results you see will vary based on the suppressor, the length of the barrel, and the ammo you\u2019re using, but tracking these variables and understanding the why behind it all will help you make predictions.<\/p>\n

Installing the piston<\/h2>\n

How handy are you? Most AK pistons are riveted to the bot carrier. Rivets suck.<\/p>\n

Look closely at the top of the bolt carrier, near the piston, and you can see where the pin has been peened over and then ground to match the profile of the bolt carrier. It will likely be a thin line that gives it away.<\/p>\n

\"Look
Look for a slight divot or line here, where the hole has been plugged and filed round. That’s what you need to drill out.<\/figcaption><\/figure>\n

A center punch here makes it easier to drill out. If you try to drill out the head, your bit may skate on the steel. Not good. Punch an indentation, then drill it out (I used a 5\/32 bit).<\/p>\n

You aren\u2019t drilling through the bolt carrier\u2014just through the tip of the rivet\u2019s top. Once that is free (you\u2019ll feel the change through the drill if you are using a hand drill), stop.<\/p>\n

Next, drift the remaining body down and out. A brass punch and a light hammer make easy work of this. This rivet isn\u2019t holding in the actual piston\u2014that screws into the bolt carrier. When the pin is out, you should be able to turn the piston by hand.<\/p>\n

To add the KNS, you simply screw the new piston back in. At its base, there are two through-holes. This allows for some of the AK\u2019s notoriously loose tolerances. Simply screw it in place, and get it far enough in to align one of those holes with the bolt carrier, then insert one of the roll pins that comes with the kit and tap it into place (a roll pin punch will make this much easier).<\/p>\n

\"The
The roll pin goes in the drilled-out hole to hold the KNS piston in place.<\/figcaption><\/figure>\n

At this point, you should be ready to go. The roll pin will prevent the piston from spinning loose. Make sure it is deep enough in, slightly counter-sunk on both sides, and it won\u2019t interfere with the motion.<\/p>\n

Dry fit your parts, and make sure everything works as intended by cycling the action a few times. If something is off, you may have the wrong length. KNS makes many, as there are many gas-system lengths in AK land (and they make other useful parts, too<\/a>).<\/p>\n

Does it work?<\/h2>\n

There’s only one way to tell. Hit the range.<\/p>\n

With the rifle back together and cycling like it should, you’ll need to test out the various piston positions to see what runs best with what you’re shooting. Keep in mind that not all 7.62×39 is the same.<\/p>\n

\"The
The new KNS Precision AK piston requires a bit of effort to install, but it is hardly complicated and well worth the upgrade, especially if you intend to run suppressed. In the end, it will have an Elftmann trigger<\/a> and a Hiperfire safety<\/a>, too.<\/figcaption><\/figure>\n

I tend to use two settings more than others–the one that works best for suppressed fire and the one that allows the gun to run reliably with steel-cased import ammo. With those two variables known, this gun has taken on an entirely new level of functionality.
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