I just put this new JT no ban M4 (please don't sue me Colt) upper on my previously post ban rifle.
Well after about 200 rds., I started having FTE/FTF. Gas key was loose. Took it to a gunsmith (I don't have my tools here in AZ) and had him restake it. Today, I shot about 200rds with no problem. While cleaning the rifle, I found that the bolts had loosened so that the stake dimples no longer lined up (aka future problem). I was thinking about taking it back to the gunsmith and have him locktite and restake in 3-4 (instead of 2) places.  
What do you think?- I amwilling to try anything.

Have him take a sharp cold chisel or centerpunch and stake the hell out of those gas key screws in 2 places.  I had this same problem on my new AR pistol and got serious about taking those damn things in place.  They're not moving now!

Anyone else have a similar problem? I plan on staking the hell out of it but what about the locktite as an added security measure?

Giving myself one last bump before this thread disappears into the depths of the second page.

Anymore input? Anyone there? Can you hear me now?

When I replaced my gas key, I first cleaned the carrier and key with brake cleaner, to remove any oils. I then put red Loctite, on the key screws, and torqued them per the T-M ( 35-40 in/lb ). After torquing, I staked the screws in 3 places, about 120 degrees apart with a sharp center punch. I put the punch where the cap screw head, and the counterbore in the key are, and hit them both in the same blow. This puts a dimple in both the key and the screw. I have fired several thousand rounds since, and there is no sign of the screws loosening. When staking the screws, make sure the carrier is sitting on a flat solid surface, and hit just hard enough to dimple the screws/key. If you use too much hammer, you risk damaging the carrier.

Gas key....  just make sure you don't leave home without it (click here).

Quoted: When I replaced my gas key, I first cleaned the carrier and key with brake cleaner, to remove any oils. I then put red Loctite, on the key screws, and torqued them per the T-M ( 35-40 in/lb ). After torquing, I staked the screws in 3 places, about 120 degrees apart with a sharp center punch. I put the punch where the cap screw head, and the counterbore in the key are, and hit them both in the same blow. This puts a dimple in both the key and the screw. I have fired several thousand rounds since, and there is no sign of the screws loosening. When staking the screws, make sure the carrier is sitting on a flat solid surface, and hit just hard enough to dimple the screws/key. If you use too much hammer, you risk damaging the carrier.

Excellent advice.  I did the same thing... key is to get it clean with gunscrubber/brake cleaner, then locktite, torque, and stake the hell out of it.  Mine that I have re-staked sure dont look pretty, but they havent turned loose in 1000's and 1000's of rounds either.

This has happened on two bushmaster bolt/carriers of mine right around the 1000 round mark... and I have not had it happen on my Colt or RRA carriers.,,,,,. of course, it just so happens I shoot the bushies all the time... and rarely shoot the others.

OK- instead of backing out the halfway staked screws, I retightened and staked each one a couple extra times- problem solved.

If I have aymore problems- red locktite, new screws, and a lot of proper staking.

Had the same problem w/ my Bushy key.  I'm going to try loc-tite and see if that  works.  Mine worked its way loose after roughly 1k rounds as well.  Good luck.
Mike, NY

I had my gas key come loose after about 1500 rounds, fortunately, I bring "range" tools with me to include a multi-allen wrench tool. I turned 'em gorilla tight and voila. I have seen this issue with others at the range as well. Now, when I clean, I also inspect the gas key screws to insure proper tightness. I consider this "preventive maintenance".

You guys... seriously need to *stake* those screws.... not just get em tight.  You dont want them backing out when you need them.