Just put together an AR build with a Colt 6920 SOCOM Complete Upper and Aero Precisions Lower. Added a Colt Buffer Tube with JP Enterprises Silent Captured Recoil Buffer Spring.

I took the rifle out to the range for the first time today and noticed that it is failing to eject the ammo casings. I have to pull the charging handle each time I fire for the casing to eject. I can immediately fire after each pull of the charging handle.

My friend was with me with his AR so we put his BCM BCG in my rifle and it fired just fine. Casings ejected normally and I had Semi Auto capability.

I'm assuming the problem lies somewhere in my Colt BCG, but wanted to get some opinions from this board on what steps I should take in figuring out the problem.

If it makes any difference, I was using Federal XM193 rounds.

Any help would be greatly appreciated.

You are calling it a rifle so I have to ask you; are you using a rifle buffer tube or a carbine buffer tube? If you're using a rifle buffer tube are you using the white plastic spacer with the JP captured spring?

JP captured spring is great (at least I like them) so you should be good there as long as you are using the spacer if you have a rifle buffer tube.

XM193 is fine so you should be good there.

Did you build your upper? If so you might want to check that your gas block is properly aligned on top of the barrel's gas port and that it is tightened correctly to the barrel.

If the spring is installed properly and the gas block is installed properly there is one other area I would check before doing any gas port modifications or things like that. And that is the bolt. Make sure that the bolt is turned correctly in the BCG. You'd be surprised how often guys inadvertently assemble their BCG with the ejector facing the wrong direction.

Best of luck.

EDIT: Just saw where you said you used a complete upper. Check your bolt.

Sorry about that. It is carbine length.

Noticed that the gas key wiggles could this be the issue? Also, does this looked properly staked?

I'm assuming that the gas key was not properly staked because I was able to tighten with an allen key. I will test it out at the range tomorrow to see if tightening the gas key fixes the issue.

Loose gas key is definitely the problem. Staking means the screws have some metal around them pushed into the screw heads so that they literally can't back out because the metal is bulging into them.

Did you read the part where he swapped bcg's and it functioned fine?

That would indicate a problem with his bcg.  Like the above poster indicated most likely a loose gas key.

You should send it back to Colt and  have them re-stake it.