Hey everyone!  I am a new member but I have been reading these boards for awhile.  I'd been wanting to build an ar for a couple years (I have been collecting guns for a long time now) and just finally got my first ar built!  I wanted to first of all say thanks for all of the great info and help that this site has given me.

Ok, now my issue.  First off, the weapon has the following configuration:
RRA stripped lower w/ DPMS lower parts kit
ACE Socom stock w/ DPMS buffer and carbine spring
Unknown A3 upper w/ 10.25" barrel on form 1
This rifle is using Colt LEO alum 30 round mags

I finally got it built and to the range a couple days ago and fired my first round out of it and it felt great.  Went to fire the second round and nothing.  It had failure to eject.  I did some research to find that little technical term for it and for anyone who is not familiar with it, bushmaster describes it as the following: When a round is fired and the empty shell casing is extracted from the chamber but is not ejected completely and upon full cycle of the carrier, it attempts to load a fresh round into the chamber.  This then squeezes both the spent cartridge and the fresh round down into the chamber side by side.  It looks similar to a double feed but one of the rounds are spent.

Bushmaster said that it could be the ejector or the ejector spring.  They suggested cleaning it or replacing it.  The thing that I don't understand is that when I did a function check, I can manually cycle rounds through the rifle very quickly and even rather slowly and it cycles great.  The only thing that I can think of is that I over oiled it since I'm not too familiar with how much oil is too much, I may have gotten carried away...plus it was a fresh build and I wanted it to absorb plenty of oil.  I pulled the rifle completely apart and found an excess amount of oil inside of the carrier.  I cleaned the entire rifle and applied a much more subtle amount of oil to the carrier this time.  I have not been able to shoot it again to find out if it helped so I just wanted to get some opinions...figured it wouldn't hurt.  I appreciate any information and I will try and dig out the digital camera (we're moving so it's packed) and get some nice pics taken and post them for your viewing pleasure.

Make sure the chamber is basically dry.

You don't have to dry it out with a hairdryer, but make sure there's not much oil in there.

What kind of barrel, and more precisely chamber, do you have? It should be marked on the barrel.

Depending on what ammo you're using, you might be shooting 5.56 ammo in a tighter commercial .223 chamber.

I'm just thinking out loud here, but check to see what chamber you have first off.

WIZZO

where exactly is the chamber marked on the barrel?  Is it under the handguards??  The barrel is a heavy style barrel...thick all the way down, including under the handguards.

Go to the M-16 forum and look for the tagged post (how in the hell do I get the 10.5 to run).

Well I went to the range today and my problem was still not solved.  I took some advice for trouble shooting the rifle and took a small piece of paper towel and stuck it under the extractor spring.  Wouldn't you know...it fired flawlessly after that.  It just needs extra tension in the spring to hold onto the spent casing.  The paper towel is obviously not a good fix as after I pumped 1 1/2 mags through it, it stopped working but it helped me establish that as the problem.

I read in the 'how the hell do I get the 10.25" running' thread under m16 about a d-fender extractor spring.  Does anyone know how long something like this lasts and what it's made out of?  I am interested in getting one and I found it for $12 but if it's cheap or doesn't work well or falls apart easily, I'm not sure if it's worth it.  Thanks.