I had a 6.8 giving me fits on a stuck bolt. Guy I bought it from said it ran fine for him. He could have swapped out bolts before selling me this gun, maybe without knowing the key had issues.

For the avg cost of a carrier, (this brand unknown) should I just replace the key per the staking instructions around? With two bolts are they pretty much self aligning when torqued down right, assuming the carrier is in spec?

Does anyone loctite the bolts? Put a dozen ARs together, just never messed with the key and very few other parts. If there's a link that covers this better, I'm thankful. I see they are about $12 on on popular AR site.

I did try that, and since the key is set back a bit from the carrier, I couldn't see it make contact with the tube. I didn't know if there was a ID, OD issue, or just mis-aligned.
When they usually put these together, do they use some sort of jig for absolute alignment? It was sticking SO bad, I had to knock the hell out of the CH just to free it.
By eyeballing it, you wouldn't have thought there'd be an issue. I kinda wished I had a cutaway upper just to SEE the frickin problem. I just hate to trash the whole thing if a new key will fix it.

Sully's pics are good.  It's hard for the gas carrier to be misaligned if its tight, unless it's mis drilled or bent. that is not likely. Throwing a new key at is is not likely to fix it.
More likely  it's the gas tube.  Take your time like Sully suggests and you absolutely will figure this out.

Sorry, I'd mentioned in more detail on another thread here what I'd done. After cleaning the chamber, bbl, bolt, etc.. I did take a bright light and looked under and from behind through the upper and the tube looked fine.
I then swapped out the whole BCG with another new 5.56 BCG I had lying around. Slid in like butter. The bolt lugs looked fine. I took the 6.8 bolt out of the carrier and just tried slipping the carrier down alone and it would stick tightly.
Not sure if the ID on the key is off some or what. I could try to dig out an extra gas tube and see if it will at least insert into the key. The key hole doesn't really look fouled up beyond normal.
Since it really sticks, I doubt it's not in line. The new carrier key was fine on the tube, so it's not the tube. It about has to be the sizing of the key unless the bolt holes are not fully inline.
I may have an extra key from a long ago Bushmaster extra parts kit.
Most of my stuff is in storage after moving. What is the normal depth into the key the tube sits? I will try to see if the boltless carrier will slip into another rifle, I suspect it won't.
I own about 8 ARs with 3 lowers still waiting, I've built all but one of them.
I'll repost soon as I get the time without the kids around. They are fairly new and young step kids that are great, just haven't been exposed to firearms as of yet. So, my gunwork usually happens when they are in school. Thanks for the pics though.

I had a out of spec AA carrier key on my factory built Grendel (they told me to clean it when I emailed them ) so it took me a bit to figure it out but when i did i installed a spare colt from my parts bin and it worked 100% after that

but my problem may not the same it was meeting resistance with  gas tube while feeding causing misfeeds so sometimes the smallest or most unexpected part can cause the problem

If I use Loctite, I use 2620 which is rated to continuous 650 degrees F., AND I use Torx Plus ASTM A574 socket head cap screws which are stronger than Grade 8, then I apply a tiny amount of Permatex Aviation Form-A-Gasket #3 to the area around the gas hole at the bottom of the key, then I torque to 55 inch pounds, finally I stake the key using a Brownells staking tool.







There is no such thing as "overkill"

Good info. I'd at least like to say I have done it once, I know how to in the future if needed. Thanks. Are those same torx bolts available at Home Depot, Lowe's, etc?

What you need to do is order from a vendor who sells only U.S. Manufactured hardware, McMaster-Carr is a reputable source.

You are looking for ones that are ASTM A574 certified.  NOT "Grade 8"!

8-32 x 1/4 Torx Cap Head Screws

Link defaults to  basic page.  Go to the high torque alloy pic and then to 8-32 x 1/4 on the left tab.
I'm impressed at the price.