I ordered a muzzle brake online and it was threaded 1/2 by 28 and said it was for .223/5.56 NATO, but since I have been having so many problems with this rifle, I looked at everything I could to see what was wrong and I noticed that the hole in the muzzle that the bullet comes out of is large enough for the .308 cartridge! Could this be a the reason that there is not enough gas getting back to the carrier to properly eject and cycle the next round?

the hole in the brake is irrelevant to the function of the rifle.

Nope. Also, .308 flash hiders are generally threaded 5/8 by 24 and would never thread onto your .223.

The holes are made larger than the bore to account for non-concentric threads.

Thanks man, I didn't think it did, nut a few other people that had bought the exact same muzzle said that it would not work for a .223/5.56, but there were about 150 other reviewers that bought it said that it worked awesome. My rifle has been malfunctioning ever since I built it, it would fire the first shot, but sometimes not eject the spent cartridge and also not fire the next bullet. I had to keeppulling the charging handle every time to fire it! But one time I shot it and only used 5.56 ammo instead of the .223 and it functioned flawlessly! I don't get it, so I am just trying to check everything possible starting with the easiest first. Thanks again for your help, I can check that off the list as what is not wrong with the rifle.

What buffer do you have?  Did you build the upper?  

Your gas port may me too small, unlikely.  Your gas block might be misaligned.  Also might be too heavy of a buffer or spring.  Or you might just need to run a few hundred rounds of 5.56 through it.