#gasblock

The adjustable gas block for the AR-15 platform has been around in one form or another for many decades now. Many people will exclusively use an adjustable gas block on each and every one of their builds…whether it’s truly warranted or not. So I pose the question…when is an adjustable gas block necessary on an AR platform? Let’s break this down and discuss some of the reasons why, how they work and then the when.

So why would someone feel the need to install an adjustable gas block on their AR platform? Often times it’s when an AR gas system is overgassed. An overgassed AR will typically wear out part much faster than a properly gassed system. This is directly related to the gas port size on the barrel under the gas block. Many barrel manufactures will rather have a larger gas port size to ensure that the firearm will function with any type of ammo. This of course will be amplified if one is also shooting that firearm suppressed. Felt recoil can feel a tad more abrupt, but the easiest way to tell whether a firearm is overgassed is by looking at the ejection pattern. An overgassed firearm will typically eject spent shell casings in the 1-2 O’clock position from the chamber. A properly gassed firearm will typically eject around the 3-4 O’clock position and an undergassed firearm greater than 4 O’clock. If a firearm is undergassed…an adjustable gas block cannot help add more gas to the system.

So how exactly does an adjustable gas block function? There are many different styles, but they all essentially do the same thing. They will have a valve or a screw that will block off part of the gas port leading out of the barrel, hence reducing the amount of gas through the gas tube to cycle the bolt carrier assembly. Some will have just a set screw that’s turned in or out, but the better gas blocks, such as those from SLR, Superlative Arms or FoxTrot Mike will have some sort of a click detent, rather than just a threaded adjustment. One look over at Brownells…one can see just how many different adjustable gas blocks there are on the market today.

So when do I recommend an adjustable gas block in normal situations? A standard AR-15 chambered in .223 or 5.56 all things being equal with a properly sized gas port typically does not require an adjustable gas block. However, if said firearm is going to be run suppressed the majority of the time, either an adjustable gas block or heavier buffer might be warranted. Now for calibers that the AR platform wasn’t originally designed for, such as 6.5 Grendel, .300 Blackout, 6.5 Creedmoor and others…I always recommend an adjustable gas block just so that the shooter can fine tune said firearm to the ammo they plan to use. An adjustable gas block can help get the most out of the weapon system when purposely building one for hunting, match shooting etc… One look at any of my “non-standard” caliber AR firearms and you will see an adjustable gas block on each and every one of those.