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Artiz
10-12-14, 21:18
Hi guys, one of my AR's (10.5" build, LMT barrel) seems to have a gas leak between the key and carrier.

I'm well aware that an AR leaks gas from everywhere during each shot, I was just wondering, since I've read many (short stroking problems) threads about lapping the key to the carrier to prevent leakage, torquing and what not, if this was considered excessive/normal or not.

The rifle runs just fine and doesn't short stroke (it has mostly been fed 5.56 Norinco ammo, 223 spec ammo definately run the action slower, but strong extraction and no short stroking) so I have no real concern to be honest. I'm just curious.

I don't mind the carbon buildup I only clean every thousand rds or so, this gun doesn't get babied and is run good every week, however it seemed to have built up quicker than usual as of late.

BCG is made by BCM. Key is solid and screws are tight.

http://i1024.photobucket.com/albums/y309/konaye4ever2/DSCN1407_zps93e6d873.jpg

http://i1024.photobucket.com/albums/y309/konaye4ever2/DSCN1405_zps6551daad.jpg

http://i1024.photobucket.com/albums/y309/konaye4ever2/DSCN1408_zps205fb4a6.jpg

Thanks.
BufordTJustice
10-13-14, 09:37
How does the key feel when you really twist and tug on it? This makes me think your gas key has a broken screw. Likely the front screw.
markm
10-13-14, 09:39
I had that happen (the front screw)... and the key still felt snug as could be. But there was a gap where gas was escaping.
BufordTJustice
10-13-14, 10:35
I had that happen (the front screw)... and the key still felt snug as could be. But there was a gap where gas was escaping.
Yeah, it happens. No biggie.

I rec complete removal and replacing both screws with some grade 8 fasteners from Grant. I would clean, degrease, and lap both the carrier and the bottom of the key. Then use some green Loctite sleeve retainer between the key and carrier. Torque the screws properly using red Loctite on the threads and then stake properly.

Let sit for 24-48 hours and then run some rounds through it. You'll be GTG.
AaronP220
10-13-14, 12:42
This is what Young Manufacturing recommends for re-sealing the gas keys.

"Here is our procedure for installing a gas key. First clean the oil from the gas key and the mating surface on the carrier. Then clean the oil from the screw threads. We use break cleaner for this. Next use a very light coating of Permatex high strength thread locker gel on the bottom of the key. PN 27010. This is much easier to use than the Permatex gasket sealer. It comes in a plastic twist dispenser. Make sure you don’t use so much that it squishes into the gas port hole. The cure rate is 60 minutes. Next coat the screw threads with the same gel. Install the key and torque the screws to 56 inch pounds. Should you decide to remove the key for some reason don’t use the old screws when you put the key back on! You will most likely break them during installation or when you fire the rifle. Go to the local hardware store and buy new 10-32 x ¼” SHCS. "
markm
10-13-14, 12:51
ESK is fond of leaving the original finish under the key and on the carrier as is sorta smooshed together to form a natural seal.

I've lapped mine lightly and sealed with a thing coat of rockset. Never been a problem either way though.
BufordTJustice
10-13-14, 13:11
ESK is fond of leaving the original finish under the key and on the carrier as is sorta smooshed together to form a natural seal.

I've lapped mine lightly and sealed with a thing coat of rockset. Never been a problem either way though.
Good to know. I'll defer to his knowledge.
BufordTJustice
10-13-14, 13:13
Also, for the fastener, Grade 8 unit from McMaster-Carr would be my highest recommendation.
Artiz
10-13-14, 14:05
Like these? http://www.mcmaster.com/#91251a338/=u4xm3r

Also, is there a particular process I should follow (screws being staked, etc)?
BufordTJustice
10-13-14, 14:24
Like these? http://www.mcmaster.com/#91251a338/=u4xm3r

Also, is there a particular process I should follow (screws being staked, etc)?

Listen to Ned on the screw size. You can stake the screws later. The green Loctite sleeve retainer between the key and carrier, and red high temp Loctite in the screw threads is vital along with getting proper torque. Let that cure and you're going to be GTG until you can get the screws staked properly.

Just make sure and fully degrease and clean both the carrier and the key. Surface prep is the foundation for proper application of any thread locker.
Ned Christiansen
10-13-14, 14:24
Screws are 8-32X1/4 and not 10-32 as mentioned in the Youngs info. If you get them from McMaster-Carr I believe you will get HoloKrome or another American brand, good deal.
TXBK
10-13-14, 14:47
http://www.mcmaster.com/#91251a190/=u4y4hd

You get 100 for $8.89 plus shipping.
AaronP220
10-13-14, 14:48
Screws are 8-32X1/4 and not 10-32 as mentioned in the Youngs info. If you get them from McMaster-Carr I believe you will get HoloKrome or another American brand, good deal.

Ahhh. Yep. You're absolutely correct.
Artiz
10-13-14, 15:50
While I'm at it I'll get the green Locktite from McMaster too. Which one tho? General purpose, high strenght, high temperature?

http://www.mcmaster.com/#loctite-retaining-compounds/=u4yycw
BufordTJustice
10-13-14, 16:42
While I'm at it I'll get the green Locktite from McMaster too. Which one tho? General purpose, high strenght, high temperature?

http://www.mcmaster.com/#loctite-retaining-compounds/=u4yycw
Loctite 620, green, sleeve retainer.

It's not as commonly available as the std red and blue types. Amazon and eBay have it.
Artiz
10-14-14, 16:32
Well McMaster don't ship out of the U.S. so I'm left with whatever I can find here.

What do you guys htink of these? http://www.wolverinesupplies.com/details/9487/Armalite-AR-10M-15-Bolt-Carrier-Gas-Key-Screw.aspx