Loading for a 5.56x45

[bat119]

I have a CZ-527 that has a 5.56X45 chamber (at least that's what the manual says) since the 5.56 is loaded to a higher pressure than a.223 Rem should I use the 5.6 data or the 223 data. I should note here that My rifle has 1-12" twist my preferred bullet is a 53 gr. V-max because I have 500 or so on hand.
I was am going to try some N133 for my first go around with this gun, my Rem VTR .223 likes Varget unfortunately I'm running low. Has anybody else tried N133 ?

 

[beltfed]

This has been done to death. With very little exception, and very minute differences between a .223 and a 5.56x45 mm chamber, the two are interchangeable.
Regardless of all of the nonsense that will likely get posted after this, you want to build loads for your rifle, not mine.
Follow several manuals, start low and build up.

 

[bat119]

Okay if they are the same why do I keep seeing this posted on the internet ?
Externally, the two cartridge cases are identical. The main differences are that 5.56x45 mm NATO operates at a higher chamber pressure (about 60,000 p.s.i. versus 55,000 p.s.i. on the .223 Rem.) and the 5.56’s chamber is slightly larger than that of the .223 Rem. Also, the throat or leade is longer in the 5.56x45 mm chamber. What does this mean? You should not shoot 5.56x45 mm NATO out of a rifle that is chambered in .223 Rem.

a .223 is loaded to 55,000 psi and the 5.56 is 60,000 psi ?

 

[Ganderite]

The 223 chamber can be cut with a shorter throat. This raises pressure. I assume (but don't know) that by now all the manufacturers use a chamber that will take 5.56 ammo. SAVAGE, for example, use a 223 chamber cut with a civilian minimum case section and a NATO throat. Although they stamp the rifle "223" it is perfectly safe with NATO ammo. The longer throat also takes the 75 & 80 gr bullets better, too.

Use the 5.46 data; start low and work up to find what the rifles likes.