.223 / 5.56 headspace gauge ?

[Keyless]

I have what may be a stupid question . Does a 5.56 and .223 use the same headspace gauge ? I am getting mixed signals from looking up the gauge. I am thinking they are slightly different and the barrel I have was listed as an 5.56 / .223 .

[dralarms]

223 and 556 are the same round. 556 is just hotter.

[Oh Shoot]

223 and 556 are the same round. 556 is just hotter.

Might be hotter, might not, as 5.56 casing might be thicker, might not.

SAAMI says 5.56 is rated to 62K psi but .223 only to 55K psi. CPI disagrees, rates them both at 62K.

Anyway, main diff is in the chamber of gun, leade (throat) is longer on 5.56 chamber. But where shoulder of casing seats is the same and length of casings are the same, so headspace should be the same, right?

- OS

[Guest sklax17]

Yes and no there are slight variances... Even though the 249 and m4 are the same caliber they have diffrent headspace gauges. As has been said that there is a higher pressure the 5.56 is created where the chamber is slightly diffrent and a little longer just slightly. With that it is like everyone heres 223 can be fired out of a 5.56x45 but not vis versa where it is backwards a 7.62x51 can be fired from a .308 but not the other way. Easiest fix get a 5.56 barrel only kidding Im not sure how interchangeable as only deal with 5.56 but I would say the gauges are different as they are calibrated to tighter tolerances than mil spec

[Dolomite_supafly]

All you need to know:

http://ar15barrels.com/data/headspace.pdf

Dolomite