I purchased a Bulgarian AK74 kit from Arms of America with an assembled U.S. barrel and built it on a Nodak Spud receiver.  I took the rifle to the range for a test fire and can't get it to cycle. When a round is fired the bolt only opens up roughly 2" typically.  I rechecked the headspace with Go/No Go gauges and everything is good.  With the FCG and the recoil spring out of the rifle the BCG will slide from chamber to rear trunnion and back by tilting the rifle back and forth.  I placed the magazine in the magwell and cycled the bolt manually with the dust cover off and its not hitting the mag.  I can blow through the gas block or fill it with fluid and it drains as well as the piston being blackened after firing a round off.  I have only tried 7N6 in the rifle as that's all I have at the moment.  The only ideas I have are that it's possibly under gased (I'm definitely not convinced this is or is not the problem), or that the hammer spring is too stiff.  If anyone can offer any advice on this I would greatly appreciate it.  Thanks in advance!

Since you are using the 7N6 I can't say it is the ammo, so as long as it i not dragging on the mag or the ejector tang I would have to agree with you it is under gassed. But before opening up the gas port I would send it back to the manufacturer to let them correct it.
There is no sense in you wasting your precious ammo to correct the problem, let them do it it is their problem.

Thanks for the response. That's really what I'm leaning towards. I'll have to give them a call and see what they say. Thanks again!

Smart move.
If you try to fix it yourself and that isn't the problem, you'll have ruined the barrel, and if the rifle is altered the maker will not warranty it.

Problem solved.  I contacted Arms of America and they agreed that it sounded like a gas problem and told me if I felt comfortable removing the gas block to go ahead and do so to see if the problem could be identified or I could send it in to them.  I removed it myself and found the problem to be that the gas hole in the barrel had been drilled .110 (further out the barrel towards the muzzle) from the gas hole in the gas block. They said if I was capable of performing the work to go ahead and they would make it up to me in a future order, or that I could send it in to them to have the work done. I was able to remedy the problem by milling a channel in the barrel to allow the gas to reach the gas block. They were very prompt in all communication and sent me a pic of what they recommended I try to do if I felt up to it. Here is what I ended up with and it works great! Thanks again for your help! http://i1156.photobucket.com/albums/p575/dragemd/IMG_1243_zps4da2b1dd.jpg