I have a Bulgarian AK74 that is a nightmare.  Sometimes rounds extract, sometimes they don't.  Sometimes it feeds, sometimes it doesn't.  Sometimes the hammer will cock all the way back, sometimes it won't.  The list goes on.  Double feeds are somewhat common as well.  I have tried it with surplus Russian ammo, wolf ammo, and some American made 5.45.  All the same.  I have tried cleaning it intensely.  I have tried changing out the magazines.  



Where should I send it to have it evaluated/fixed?

Try Mike Friend at the Firing Line

Troy Sellars at InRange has done good work for me.

http://www.inrangec2.com

Both Mike & Troy come highly recommended. I use Nick @ Beeville Armory
www.BeevilleArmory.com