AR15 gas tube slightly touching gas key aka Binding

y2k

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I would not say the bolt binds but i can feel it when bolt key comes in contact with gas tube. Very slight contact but just can`t quite stop it from contacting the key when moving the bolt with finger ( upper remover from lower) maybe I`m over reacting? when upper is placed at 30 degree angle bolt falls into locked (closed ) position easily.
 
The tube need to touch the key or more precisely be inserted into the key to form a seal, otherwise the pressurized gas will just escape from the gap instead of pushing the bolt back to cycle the action.
 
That is normal. If the bolt carrier can fall out freely, this means the gas tube and the gas ring are worn out. The gas tube has a bulb at the end, low quality gas tubes worn out quicker and the bolt carrier drops out the lower with no resistance after fairly low round count.
 
My bolt assembly when upper is canted at about 30 degrees with fall closed and lock up. Its just when I move bolt assembly with finger i can just lightly feel it when contacts gas tube ( bolt key contacts gas tube)
 
Take a look at the barrel nut. The gas tube should not be pushed to either side by the notch of the barrel that it goes through. It should be aligned with the gas tube hole in the upper.
 
Take a look at the barrel nut. The gas tube should not be pushed to either side by the notch of the barrel that it goes through. It should be aligned with the gas tube hole in the upper.

This^^^
If it's centered and you're not getting malfunctions then don't worry about it.

Is the inside of the gas key chromed? Sometimes they get a little tight if the key was built to spec then chromed afterward but it shouldn't effect anything and they should wear in nicely after a few hundred cycles. A snug fit is a good thing as it will get a better seal.
 
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