Carrier gas key & gas tube interference

[Bill Bryant]

In his excellent thread Quib tells us that the "carrier gas key should engage gas tube with no noticable resistance":

http://www.weaponevolution.com/forum/showthread.php?p=13881#post13881

I'm wondering what should be considered "noticable resistance." When I do the test and let the bolt carrier slide on its own, I can't tell when it engages the gas tube. When I assist it with my hand, I can just feel the spot where the carrier key and gas tube first meet. There's a little tick or click, the carrier key shifts its position ever so slightly, and then it slides on down. I've just built my first AR and have no idea what the Go/No Go point is with regard to this interface. Can't feel the point of contact at all? Can feel it but not any additional drag thereafter? Can feel it but gravity pushes it right on through every time? Won't go on down without a shove?

I've had my rifle out in the woods and it ran without a hitch. Still, my engineering/machinist side is curious.

[Quib]

If the carrier key glides effortlessly onto the gas tube, then you are fine. If the carrier key contacts the gas tube, and must be pushed by hand the rest of the way into battery, and the gas tube can be observed giving way to the carrier key, then adjustment would be recommended.

[Bill Bryant]

That's what I was hoping to hear. Thanks for the quick reply. I'm good to go.

[Quib]

If enough time and attention is invested in adjustment, the carrier key will not contact the gas tube at all.

A tip to knowing which direction to adjust, is to get a Correction: Dark Colored Marker or Paint Pen, and color the lip of the carrier key opening.

By sliding the carrier into the upper by hand, to the point of engaging the gas tube, the Colored Marker or Paint Pen will be worn away in the area of contact. This will then indicate which direction the gas tube needs to be adjusted.

ETA: As time permits, I’ll add the adjustment procedure to that thread.

[Bill Bryant]

How do you move the gas tube if this is needed? Specialized tool? ViseGrip? [:)]

[Quib]

Initial adjustments can be made by applying slight pressure to the gas tube in the area above the barrel. Sometimes this adjustment is all it takes.

Finer adjustments can be made within the upper receiver by applying slight pressure against the gas tube with a non-metallic item. This works for adjustment to the L, R and Up.

A loop of 550 cord dropped around the end of the gas tube, then wrapped around your hand, helps when the tube needs to pulled down towards the direction of the magazine well.

[Blankwaffe]

Quib,
Outstanding work as usual.
Post up the staking pictoral as well.

[Quib]

Thanks BW. [:)]

I plan on adding my DIY “Carrier Key Staking Procedure“, but would like to re-shoot the series of photos first.

[Bill Bryant]

What if the gas tube is fine and it's the carry key that's crooked?

[103m 95g]

What if the gas tube is fine and it's the carry key that's crooked?

contact a site sponsor such as, Rainierarms.com or BravoCompanyusa.com and purchase a new key

[Quib]

What if the gas tube is fine and it's the carry key that's crooked?

The -23&P addresses how to correct small dents and/or distortions in carrier key. Personally, I think the best bet would be to replace the key as previously stated.