I was cleaning my colt AR-15 (PREBAN) last night and noticed that the carrier key was loose on the bolt carrier.

I tried to tighten it, but the screws are still locked in place and will not turn.

Anyone have this happen to them?

SC,
Yes.It has happened with alarming regularity lately in the new M4's we get at "Work".

There is one and only one cure.
Shitcan the gas key that is loose.
Mount up a new one(With new screws),torque to spec(As listed in the TM) and stake the thing as listed in the TM in 4 places.
It's been observed that the use of Permanent locktite on the threads is also advisable.

The new 2 place staking by Colt and Bushmaster ain't working out so well.
Both companys seem to be lacking in QC in this regard lately.

Best of luck to you!
S-28

Ditto with Armalite.

Seems to me the gas key could be reused, assuming the screws can be removed without damaging it.

As temporary fix, I’d try cranking the screws down tight and just checking them during each cleaning.

When you get a chance, get new screws, replace the old ones, and then stake them securely per the TM.  Remember that technically the screws need to be torqued down to the correct specs (which, IIFC, is in inch/pounds).

AND, make sure that the screw heads are deeply knurled so that the staking bites into the knurling of the screw head. I had a brand new Bushmaster carrier w/key that loosened up after a few hundred rounds. The staking looked perfect but the marks on the screw heads were nothing more than cosmetic etching and the screws both loosened up.

I toss the Gas key on account of the potential for irregular wear having taken place on the loose key during fiiring,and the potential for the shoulder that stops the screws,being worn uneven.

It's a "Double safe/when in doubt toss it out" thing.

I'm sure many thousands run fine after coming loose and getting re-torqued and staked.

However,if my name is on each and every one that leaves my armory daily,and my employer demands me to be as anal about things as possible,I have no choice.
It's one less potential variable I have to concern myself with.

My guys and their rifles come first,we have the budget to support it,and little room for apologies and explanations after a failure.

It's a perspective thing.

All the beat to all you guys.
S-28

Guys-

I just had the same problem on my Bushy that I fixed (i hope) yesterday.

The factory stake marks were practically cosmetic. I took a center punch to it and whacked the crap out of 'em - good solit marks that clearly extend to the screw. I'll take a picture later. It really seems like this whole thing is a design flaw. There has to be a better way to secure these screws.

When shooting today, I had a few FTFs after shooting about 300 rounds, so I'm not sure if my mods "took" completely. LocTite is next.

NoVaGator,

The Factory staking is kinda weak.
I really think it's a production speed compromise.

I have hollered at Bushmaster about it in the past and got back a rather glib answer stating that their tolerences were thus and so,and it couldn't happen.All the while I was staring at about a dozen rifles with floppy Gas keys,and stakes that resembled the efforts of a starving, Ebola stricken,Hippie trying to bite the gas key.

After hollering again a bit further up the food chain,and reminding them of the volume of sales we represent,I got a more logical answer.

"It happens and we apologize".

I can live with that.

The answer is to follow the field staking instructions in both the Army/Air force and USMC TM.From there,there should be no problems.

Locktite is great stuff,but it does degrade with heat.Heck,heat is the method used to release it's death grip on a fastener.
Bolt carrier keys get hot.

Sometimes after staking it takes a bit of Carbon to seal the key from what I have seen.

Go burn up another battle pack and call it Maintenence! ;)

Then again your stoppages may very well be caused by something other than your gas key repairs.

Good luck to ya!
S-28

Makes sense to me!  Kinda done that myself.

Back when I worked for the federal government, I’d toss a part as soon as look at it.  It cost the government less for a new part than to pay my salary to try to salvage a used one - to say nothing of the possible consequences of that repair failing!

But nowadays when I replace a part, I’m on my own time and I have to pay for it myself - so I try to recycle the old one if I can.

As you say, it’s a perspective thing!!

Stay safe!