.223

[Thumpa]

I'm a little confused. Aren't the .223 Remington and the 5.56 x 45mm NATO the same cartridge? Heavier bullets listed for the 5.56, is it because of barrel twist?

 

[Steve in PA]

Actually, its the chamber of the rifle that is the determining factor.

5.56mm may use longer and heavier bullets and the chamber will have a longer leade or throat for this reason.

.223 ammo can be fired in a rifle chambered for .223 or 5.56mm, however 5.56mm ammo might not be able to be chambered in a rifle with a .223 chamber due to the lack of the leade.

 

[Thumpa]

Thanks Steve, that explains it perfectly.

 

[jem375]

I shot hundreds of 5.56MM through my 223 barreled rifle with no bad effects but stopped and only shoot 223 now...

 

[Fumbler]

Don't forget, the maximum pressure for 5.56x45 is higher than 223 Remington. A lot of cheap 5.56 is loaded to 223Rem pressure, but I wouldn't risk shooting any 5.56 in a 223 Rem chamber.

Heavier bullets listed for the 5.56, is it because of barrel twist?

Twist rates in guns are determined by what the gun was designed for. Since most 223s are varmint guns, most of them will have slower twists.

 

[Hatterasguy]

You can probably get away with shooting 5.56 through a .223 barrel but I wouldn't try it. The cheap 5.56 is loaded light, but the M855 and 70+ grain stuff isn't.

 

[Thumpa]

Thanks for all your input gents, never shot either but always wondered.

 

[JohnnyOrygun]

Just a note, need to look at the manual that comes with the gun or the gun itself. I recently purchased a mini-14, while its sold as a 223, in the manual it states that it is fine to shoot 5.56 ammo also. I realize the OP didn't really ask that, but if someone looks at this thread might be helpful. Just my .02
John