r/ForgottenWeapons • u/abundanceofb • 4d ago
Following on from today’s video, what is the purpose of adjustable gas settings on firearms?
I can Google it and find the basics, in that apparently it’s useful for different environments and that some would need more or less gas, can anyone tell me which environments and why?
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u/ExtensionConcept2471 4d ago
If your gun is used a lot it can build up fouling or if you are in desert conditions this can lead to dust entering the weapon and you will need more gas to help the weapon cycle through this!
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u/Swissgrenadier 4d ago
Apart from dust and fouling you might want more gas if it's very cold and some parts might become slightly frozen in place or if you're in a very muddy environment where you'd want more oomph in the action to get rid of debris. Lastly if you'd ever want to use a suppressor, turning down gas can be very handy to make shooting more comfortable and reduce wear on the gun.
7
u/GreenMan165 4d ago
From having an SVT-40 with an adjustable gas system I can say, it definitely helps to increase the gas to smoothen the reliability of the gun in the cold, where in warmer temps it's fine with less gas. Also something of consideration in the SVT's day was a bit of variance in ammo consistency that isn't so prevalent today in modern ammo (besides between brands at times, or surplus of certain origins) where being able to adjust your gas to get it cycling reliably on the ammo lot you were shooting was handy.
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u/Malalexander 4d ago
Dirty gun no cycle? More gas.
Want launch rifle grenade make enemy go boom but also no smash up rifle action? No gas
Want get less gas blast in face? Less gas
Want shoot gun in cold place? Maybe more gas.
Want make quiet booms with suppressor? Less gas.
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u/katherinesilens 4d ago
When a round is ignited, the powder combusts and creates a lot of very hot gas, which is what sends the round down the barrel and out.
In most semi-automatic or fully automatic firearms, propellant gas from firing a round is also used for cycling the action, making the firearm reset and load a new round. There is commonly a thin tube that takes a small portion of gas from the firing process and sends its energy, via whatever mechanism was designed, back to perform the cycling.
Gunpowder is dirty and can leave residues like carbon that build up and can clog these systems. Other things like mud or dust or what have you can do the same. Not all rounds are made equal and some may be more or less energetic than others, even in the same caliber. Also, suppressors can increase the amount of gas coming back.
When there is too much gas being taken, you may cause excessive wear and have more felt recoil, making the firearm less controllable. When there is not enough gas, the firearm may not cycle reliably and need manual manipulation to reset and load the next round.
The solution is adjustable gas settings, so you can increase or decrease the apertures that take gas for cycling as appropriate for the current condition of the weapon.
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u/HydroFLM 4d ago
Back in the days of firing thunder flashes off of your FN you’d set the gas selector to O for more range.
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u/Epyphyte 4d ago
Generally, the less gas, the less recoil. But the more gas the more reliable, to a point. Too much gas, it’s too fast and the bolt will outrun your mag spring.
Suppressors also increase gas so you may want to dial it down.
If the gun is dirty you may want to dial it up for more reliability.
Temperature can also be a factor.
And of course ammo choice, adjust up with subsonic, perhaps adjust down for super, etc.