What is a "gas key" for?

This is a discussion on What is a "gas key" for? within the Defensive Rifles & Shotgun Discussion forums, part of the Related Topics category; Probably a dumb question....

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Thread: What is a "gas key" for?

  1. #1
    Ex Member Array AdBro's Avatar
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    What is a "gas key" for?

    Probably a dumb question.

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    VIP Member Array Thunder71's Avatar
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    In regards to what?

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    Ex Member Array AdBro's Avatar
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    On a gas-fed rifle. I was reading about 'staking' the gas key. I had no idea such a thing existed until I read that. I know where they are located via pictures I saw and because I took the rifle apart when I first got it, but I have no idea if I need to touch them or what they do!

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    Distinguished Member Array kapnketel's Avatar
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    You do not need to touch them. Here is how it works:

    The main mechanism of operation for the rifle is known as direct gas impingement. Gas is tapped from the barrel as the bullet moves past a gas port located above the rifle's front sight base. The gas rushes into the port and down a gas tube, located above the barrel, which runs from the front sight base into the AR-15's upper receiver. Here, the gas tube protrudes into a "gas key" (bolt carrier key) which accepts the gas and funnels it into the bolt carrier.

    The bolt and bolt carrier together form a piston, which is caused to expand as the cavity in the bolt carrier fills with high pressure gas. The bolt is locked into the barrel extension, so this expansion forces the bolt carrier backward a short distance in line with the stock of the rifle to first unlock the bolt. As the bolt carrier moves toward the butt of the gun, the bolt cam pin, riding in a slot on the bolt carrier, forces the bolt to turn and unlock from the barrel extension. (The gas system only serves to unlock the bolt while the projectile has long exited the barrel). Once the bolt is fully unlocked it begins its rearward movement along with the bolt carrier. The bolt's rearward motion extracts the empty cartridge case from the chamber, and as soon as the neck of the case clears the barrel extension, the bolt's spring-loaded ejector forces it out the ejection port in the side of the upper receiver. The bolt is much heavier than the projectile, and along with the recoil-spring pressure inside the stock buffer-tube performs the cartridge ejection function and chambers the following cartridge.

    Behind the bolt carrier is a plastic or metal buffer which rests in line with a return spring that pushes the bolt carrier back toward the chamber. A groove machined into the upper receiver traps the cam pin and prevents it and the bolt from rotating into a closed position. The bolt's locking lugs then push a fresh round from the magazine which is guided by feed ramps into the chamber. As the bolt's locking lugs move past the barrel extension, the cam pin is allowed to twist into a pocket milled into the upper receiver. This twisting action follows the groove cut into the carrier and forces the bolt to twist and "lock" into the barrel's unique extension.
    I'd rather be lucky than good any day

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    Ex Member Array AdBro's Avatar
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    Okay. I understand how the action works, I just didn't know if the "key" is something that I need to worry about.

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    VIP Member Array jonconsiglio's Avatar
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    The key just needs to be tight and staked to create a seal.
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    VIP Member Array dukalmighty's Avatar
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    Quote Originally Posted by jonconsiglio View Post
    The key just needs to be tight and staked to create a seal.
    "STAKING" is where a tool or chisel drives the surrounding metal into the screw head preventing it from vibrating loose,if the screws become loose it allows gas to escape and the bolt will not cycle right causing the gun to jam
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    How often should I check that it's staked properly? Do I know I need to restake it if it's loose?

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    The staking is the indentations on the side which keeps it from unscrewing. Some stakes are "good" in that there is typically an obvious pinch, which will noticeably prevent them from unscrewing. There are others that look like decorative dents on the top. If you google "properly staked gas key" and "poorly staked gas key" in their images section it will help.

    There was also an AF15 buyers guide that I read when I was shopping that showed the difference between the two but i can't find the link.

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    VIP Member Array varob's Avatar
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    Quote Originally Posted by AdBro View Post
    How often should I check that it's staked properly? Do I know I need to restake it if it's loose?
    No if the two screws are properly staked you should never need to mess with them. The process of staking keeps the screws from backing out.

    Just clean the outside when you clean the BCG, thats all you need to do.

    I just blow a little air in my gas key after cleaning it to make sure no solvent is in it.
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  12. #11
    Ex Member Array AdBro's Avatar
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    cool, thanks

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    Distinguished Member Array kapnketel's Avatar
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    A pipe cleaner does wonders in the gas tube also.
    I'd rather be lucky than good any day

    There's nothing that will change someone's moral outlook quicker than cash in large sums.

    Majority rule only works if you're also considering individual rights. Because you can't have five wolves and one sheep voting on what to have for supper.

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    Quote Originally Posted by kapnketel View Post
    A pipe cleaner does wonders in the gas tube also.
    Good way to get a obstruction in your gas system and not really needed to clean it.
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  15. #14
    Distinguished Member Array kapnketel's Avatar
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    Quote Originally Posted by rocky View Post
    Good way to get a obstruction in your gas system and not really needed to clean it.
    Hadn't thought about that. I started using a pipe cleaner in the gas tube when I was shooting a 22 conversion kit, I had received advice that since the conversion bolt is not gas driven, the gas tube needed cleaning. Sold the kit, old habit with he pipe cleaner. Thanks
    I'd rather be lucky than good any day

    There's nothing that will change someone's moral outlook quicker than cash in large sums.

    Majority rule only works if you're also considering individual rights. Because you can't have five wolves and one sheep voting on what to have for supper.

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    Senior Member Array Skygod's Avatar
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    Now, somebody explain "gas rings"..................
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