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Language Lessons: Overgassing
Alexander Crown
TERM: Overgassing
AKA: More Blowback, “Ouch my face/eyes”, “I can’t breathe”
CATEGORY: Shooting Terminology
APPLICATION OF USE: Referring to guns that operate via a gas system when there is too much gas. Very significant with regard to the use of silencers.
DEFINITION: The term overgassing describes the effect of gasses being expelled from a firearm to the point of the shooters impairment or to the detriment of the weapons itself.
INTO THE WEEDS: Almost all modern weapons operate via some type of gas system, some more efficiently than others, and some that are overgassed from the start to insure reliability. One of the most common forms of overgassing, besides too much Taco Bell, comes from the use of silencers. A silencer’s job is to capture gasses in order to quickly cool them and not allow them to explode into the air making a loud noise. When a silencer does its job it can force the gases back into the host weapon.
The best and most common examples of this are short barreled AR15s. Silencers increase the gasses going back into the gas tube, causing excessive wear on the gas rings, firing pin retaining pin, and buffer, among other parts. This wear is noticeable over a period of time but more immediate signs can be seen in increased dirtiness on spent brass and magazines.
Gas piston weapons can accommodate the increased gasses easier, in most cases, by either having an adjustment selector (SCAR 16/17) or multiple positioned system (FAL). These help with controlling gasses going back into the weapon by bleeding them off. AK-type weapons are usually overgassed but rather than looking at this as a flaw it’s sold as an increase in reliability. However, a suppressed AK can beat the shit out of itself and gas the user into unconsciousness.
In order to compensate for the increased gasses, particularly in AR15-type rifles, several products exist. For a decent period of time the best course of action was to increase the buffer weight to H, H1, or even H2. The purpose of the heavier buffer is to slow down the bolt carrier back to unsuppressed levels, which in turn would increase suppressed reliability. This works OK as long as the silencer is always attached.
A slightly better option has been an adjustable gas block; these vary from manufacturer to manufacturer. Some are as easy as a switch, a la Noveske, and others use a set screw to increase or decrease the amount of gas allowed into the gas tube. Gas blocks aren’t a bad option if you are able to do the swap yourself and take the time to tune the set screw to operate correctly with your system.
The last option I want to touch on is adjustable bolt carriers. Several companies have released carriers that are adjustable in some way and, as they are a site sponsor and I work for them, I think I’m some way obligated to mention Gemtech. The Gemtech Suppressed Bolt Carrier is a two position system (Suppressed/ Unsuppressed) that simply replaces your existing bolt carrier. The suppressed carrier bleeds off gasses via a port in the side and vents them out of the gun and away front the shooters face. Adjustable carriers are a good option for mitigating overgassing.
IN SUMMARY: Overgassing is simply when the weapon has too much gas. This usually can be attributed to ammunition, a silencer, or a design flaw. Understanding what happens to your weapon when a condition is changed is paramount for reliable function. Overgassing situations can be avoided in most cases by changing the host weapon or modifying it.
Question for the readers: What weapons have you fired that had a noticeable overgassing? What caused this issue and what did you do to fix it?
-Alexander Crown
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I have a 12.5″ bbl SBR that became pretty obnoxious when I put an AAC M4 2000 on it. Every bolt cycle was like a slap in the face.
I achieved a noticeable reduction in blowback by switching to a heavy tungsten core buffer. While the heavier buffer has not eliminated the issue completely, I think for the cost of the exercise it’s a reasonable improvement. I shoot suppressed almost 100% of the time so this option suited my circumstances.
I’m considering a piston conversion but in the event that doesn’t happen I’ll definitely look at the adjustable bolt carrier.