Question about 5.56 and .223 Ammo

[Principal Skinr]

Two quick questions, as I have ARs in 5.56 and .223.

The first question is how much of a performance difference is there in the velocity of typical ammo, if any? Is it a couple hundred fps?

I've read that using .223 in a 5.56 chamber results in slightly less accuracy. If so, just how much is accuracy typically degraded?

The reason I'm asking is to decide which way to go with my ammo stash. I've mostly got .223, but have added some 5.56. If there is negligible or no degradation of accuracy using .223 in a 5.56 gun, then I'll go more in that direction. (Partly because I like PMC for accuracy, and Silver Bear for cheap ammo with decent accuracy, and both are .223.)

 

[Mr. Habib]

I don't believe that there is any performance difference between 5.56 and .223. The 5.56 pressure spec is higher, but it is also measured differently. There is no direct correlation between the military spec and SAAMI's. As to accuracy, the only meaningful difference between the two chambers is the freebore. While it might have some effect on accuracy, unless you are shooting at 600 yards at Camp Perry you probably won't see enough to care. I have personally seen and shot rifles with a 5.56 chamber and .223 ammo that would consistently put ten rounds into less than 3/4 inch at 100 yards all day long.

 

[mcwulf30]

Quick question though. I'm building an AR. Do I need to headspace for a 5.56 in order to shoot both .223 and 5.56?

Or do I just headspace for .223?

 

[Mr. Habib]

That would depend on which round your barrel is chambered for. The gauge should match the chamber.

 

[Indybeer]

You can shoot .223 in a 5.56 but you shouldn't shoot 5.56 in a .223 due to the casing and press specs. It will work but you are asking for trouble.

 

[c3d4b2]

There is some info on this sight regarding different .223 chambers you might find interesting. (there is a bunch more reloading info on this page also). To get to the page with the info you will need to click on the Reloading Stuff button.

NJ Hipower Rifle

 

[HmDBrian]

Yes Indybeer nailed it, just read up on this about an hour ago actually due to the fact im buying an ar-15 on thurday. The 5.56 has to much pressure behind it to shoot in a gun that is meant for just .223

 

[Streck-Fu]

5.56 NATO is a defined specification whether M193, M855, etc while .223 Remington is a more flexible or general round. The 5.56 implies a specific case specification, particular bullet, as well as powder and primer.

 

[loony1]

Info. overload
5.56mm NATO versus 223 Remington Chamber Differences - M4Carbine.net Forums

 

[Mr. Gadsden]

Why does Bushmaster recommend against higher grain 5.56 rounds in their 'sporter' models even though it is chambered for that gauge?

I know the answer is chamber pressure, but why wouldn't they make something with a higher tolerance? Price?

 

[exelh]

Why does Bushmaster recommend against higher grain 5.56 rounds in their 'sporter' models even though it is chambered for that gauge?

I know the answer is chamber pressure, but why wouldn't they make something with a higher tolerance? Price?

It could be because of the barrel twist in a bushmaster. Slower twist barrels make it harder for heavier bullets to stablize.