re: ***UPDATE NO.3**My new AR is cycling .223 fine but hanging up on 5.56

No disrespect but you guys seriously need to either do some research or just take your rifles to a qualified gunsmith.

FIRST thing OP needs to do is find out how this barrel is chambered. 5.56 and .223 are not the same thing. Without writing a page on info you can get from Google, the 5.56 chamber leade is "longer" which means you can safely shoot .223 in it but not vice versa. Meaning if he has a .223 chambered barrel he can be subject to unsafe pressures when firing 5.56. Someone should have discussed this as soon as he mentioned that he is interchanging rounds.

Next, 5.56 is generally mil spec ammo with much harder primers. Instead of the aforementioned bolt closing issues, I would check assembly of the hammer spring to see if it is oriented correctly first. Incorrect placement of the spring legs will result in half power hammer fall and failure to ignite mil primers. Common mistake by home assemblers.

That being said, if this is a headspace issue then you have a potentially dangerous situation. Remember that you are holding a metal tube up to your face and initiating explosions at thousands of pounds of pressure. Not something to be treated lightly.

Check the chambering, verify correct assembly of your fire control components and then send the rifle to PSA or a gunsmith if headspace is suspected. Not to be insulting but this isn't something a first timer should be fooling with.

BTW, buffer weight and spring rate diagnosis is called for with regular malfunction issues such as bolt over case, double feeds and failure to chamber. Not what he is describing here as a caliber specific malfunction. I am pretty sure this is a FTF related to the hammer spring.