Hello everyone I am in the process of building my 300AAC blackout and last night I was doing some checking. and the headspace is off on this rifle, I am used 2 different bolts and still the same thing, they will lock with no round inserted into the chamber but as soon as you put a round in the chamber it wont even start to twist the locking lugs in place. if you get violent with it it will lock a round into the chamber but its a PITA to remove and the round wants to stick into chamber. I was wondering if they make a bolt that the locking lugs are shorter. or do I need to have a smith fix the barrel, I contacted the company I bought the barrel from but I have the feeling they are going to tell me I am on my own.

Sounds like a good reaming job would solve those issues. There might be extra material on the feed ramps or inside not letting you lock it up.

Are you using reloads or factory new ammo?  I have found that with a lot of barrels these days 5.56 and 300 that until broken in they wont shoot reloads.  I had the exact sale experience that you are describing.  In specific I was using a
Sota Arms 16" 1:8 twist 300 AAC black out bbl that I bought Here  
I was unable to find ammo so I got some reloads from my friend.  The reloads would stick in the chamber.  When I called my friend he said he was running them with no problem.  We then checked the rounds with a chamber gauge and they rounds showed to be in spec.  I then found a box of factory 300 ammo at gander mountain Here but it is always sold out.  The ammo ran fine.  I then found the freedom munitions reloaded ammo Here about 12 cases of 500 left.  
The Freedom munitions runs great and I am getting 1-1.5 MOA groupings.  I hope to get better in the gun vise.  

I have been playing with 5.56 for a while and have had the same issue with my reloads not running in new bbls even when they spec out.  I was told by one of the manufacturers that when they are reaming the bbls if you get a chamber that is on the small side of the specs and reloads tend to me at the max size then you will have problems until your chamber breaks in.  He also told me that many ammo companies build their ammo to the small side of the specs or just under the small size so that there are no feeding problems.

I talked to a local smith today and he said they could rent a reamer and fix it but it would cost about as much as a barrel was new.

I am using reloads, I checked all local gunshops for factory 300aac blackout ammo and none of them had anything, and yes its something I could order but for a little over 1.50 a shot I would like to use reloads as much as I can plus I have components laying around, so I checked my ammo specs and they are right on all specs I have found, but the smith told me I could neck the case down a few thousands of a inch and then check for function and continue until i get one that works, so it looks like I may have to do this to start. unless I feel like dropping some coin on a new quality barrel.

Try this:

Take a sized .300 BLK empty virgin brass case, a 2-3 Inch long machine screw and then screw than in to your primer pocket/flash hole, then remove the head
of the machine screw (cut it off or grind it off) so you only have the shaft of the screw exposed (boy this sounds erotic ! LOL) then put some liberal amounts Flitz
compound/polish on the exterior of your sized virgin case then chuck that screw shaft w/ case Into your electric drill and polish away a using short In/Out strokes
till everything is nice and smooth...You will of course need to clean out the polish/compound residue a few times till you get a round to chamber properly.

Good Luck.

If your reloads are using cut down .556 brass check the wall thickness of the necks. Some .556 brass is thicker in the body and when you form it into blackout brass it's too thick and can bind once a projectile is loaded in the case.

The solution is to turn the necks down or use a differnt brand of brass. Yours may vary but mine won't chamber rounds with neck thickness larger then .012.

An easy check to to take a loaded round, paint it completely with a black sharpe, then try to chamber it once it's dry. When it starts to give you resistance pull it out and see where the sharpe rubbed off. That's where your issue is.

thanks for the great ideas guys I will give them all a try some evening this week thanks alot for all the help!!

I have found that after a few hundred rounds the chambers seem to break in and my reloads worked.  Another thing I did was after the round was loaded I ran it back through the full length sizing die.  I removed the decapper of course.  What I found was that somewhere in the process I had a few rounds that had gotten a little out of spec.  The rounds still checked good in the gauge but after I sized them down everything was good.