My friend recently acquired a M16A2 1-7" Colt HBAR upper, I do think that it's one from the Tapco surplus kits.  Well when shooting it at the range it failed to eject every round shot through it (about 60+, both SS109 reloads (with 22grn, 22.5grn and 23grn of AA2200) and Remington factory).  

The case would rarely get pulled back at all and would have to be manually ejected by pulling the charging handle back, the spent case would rarely bind or jam on another round in the mag(maybe 5 times total it would make it back that far).  So it seems that the ejector is ok (it's a brand new bushmaster complete bolt carrier and assembly).  The gas tube is clean also, Remington action cleaner flows right through and into the barrel.  Could the problem be from a rough chamber?  I do believe that the colt has a chrome lined chamber, would a bit of JB paste in the chamber fix this??  Or are there any other ideas for this problem?

This happened to me too with a brand new Bushmaster M4 16" upper w/ Bushmaster Bolt/Carrier group.  The problem was that the gas key bolts that hold the gas key to the bolt carrier came loose because Bushmaster does a half-ass job of staking the bolts (compare the stake marks on a Colt b/c to those of a Bushmaster...you will see the difference).  The lose gas key allowed gas pressure to escape from the area where the gas key meets the bolt carrier.  This resulted in insufficient pressure reaching the gas rings, so the bolt failed to eject every round because the carrier never traveled far enough back.  The rifle was essentially a straight pull bolt action until it put locktite on the gas key threads and tightened them back down.

One sidenote, it is generally advised to replace the bolts in this situation because they have been hammered by the loose gas key, and are allegedly more prone to sheering.

 Slt223, that is the simptoms exactly, it's turned into a straight pull bolt action.  I did try my colt bolt carrier and bolt and the same problem occured.  I have his rifle and compared the bolt carriers on the bushmaster and the colt.  Both gas keys are in the same place and the Bushmaster's key is solidly staked on.  I agree, I would have thought that to be the problem, but it seems not to be.  There must be either a gas leak somewhere or a rough chamber maybe.  Any suggestions of what to direct attention to?

Some other things to consider would be the recoil assembly.  Makes sure the buffer goes all the way back, and is unobstructed.  Also, does the b/c assembly freely slide back and forth in the upper?  One more thing, check the gas rings.  Make sure none of the end gaps are aligned with those of the other rings.  This would allow exhaust to pass out of the bolt carrier with out generating sufficient pressure to make it reciprocate.  If it is none of these, I would lay blame on the gas tube or the gas port.  

If the gun has a rough chamber I would think you would be able to notice the excessive burring by comparing your firend's chamber to the chamber of a gun that is known to work.  Sorry if I have repeated stuff you already know/have tried.  Hope you get that rifle operating smoothly.