Bought a used M4 Bushy flatop upper 14.5" with post ban break by KKF - overall it looks to be in very good condition - there was no carbon build up on the bolt/carrier.  Took it out for the first time.  All I had was crappy wolf ammo but just wanted to shoot only a couple of rounds.  When fired, the bolt only cycles about halfway back failing to eject the spent shell and failing to cycle a new round.

* Does this sound like a problem with the gas tube?

* Could this be due to the steel case and coating that wolf uses with their ammo?

I am going to prebanize this upper with a forged front sight tower with bayo lug and the newest vortex flash suppressor and figured I'd replace the gas tube when I have all this done (going to get a FF KAC RAS as well just have not decided between the regular M4 and the MRE versions).  

* Does it sound resonable to expect that after the modifications the upper should run fine (considering that I might as well replace the gas tube)?

BTW:  Are these mods something tha I should be able to complete myself?

Probably the wrong forum to be asking, but I would start by checking alignment with your B/C and gas tube, then would check my carrier key making sure it isn't loose.  Sounds like gas is bleeding somewhere to me.

Does it cycle by hand?  Is it lubed?  Any idea how many rounds through it?

I had the same problem w/brand new H-bar failing to chamber rounds properly / jamming.
Put up with it untill I got my collapsible stock in . after changings stocks and buffer tubes it has been perfect since.
might look at that end also. good luck .
Gopher711

What the prev said, but also hand cycle the weapon and see if you feel the bolt head catching like it might have a burr. Make sure that the bolt head cotter pin isn't damaged.
It can also be a combination of these on other things. Personally I'd check it out and if nothing is obvious and easy to correct, call bushmaster and they will help you out by having you send it back.
Good luck, Jack

There's no carbon build up because you're not getting any gas in the action.  [;)]

It's a Bushy...check the carrier key to be sure it's tight.

If that's not it, go here...

[url]http://jobrelatedstuff.com/forums/announcement.html?b=3&f=66&id=184[/url]

Let's start with the basics.  Did you properly lube the bolt/bolt carrier?  Try some cleaner ammo first and see if that works better.