5.56 when my FAC says .223

[MarinePMI]

IIRC, 5.56 is also loaded to a higher chamber pressure (62k IIRC) than standard .223 (which is 55k IIRC). Going off memory here on the actual numbers, so TIFWIW.

The big difference is the chamber, with the 5.56 having much more free bore, to alleviate the abrupt pressure curve of the hotter 5.56 loading (kind of like what Weatherby does for their chambers/cartridges). Most AR's (and some bolt guns) these days come with a Wilde chamber for this reason, which is a hybrid of 5.56 and .223 chamber specs. Hybrid in that it retains the tighter .223 chamber tolerances for the body of the case, while also having the free bore/lead of the 5.56 chamber to alleviate pressure spikes with the hotter ammo. This is why (if you have the right barrel twist) 5.56mm ammo is perfectly fine in many/most rifles/pistols. IIRC, some European made guns are tightly made to .223 specs (which honestly, is kind of dumb), and so, 5.56 ammo may not be recommended in those firearms.

Slowly, but surely, most firearms manufacturers are migrating their .223 rifles to a Wilde chamber spec (or something similar).

 

[Bowland blades]

Mine says 224cal

That shows what firearms licencing really know . I have asked for another 6mm either i am getting another 243 or a 6 creed or even a 6 arc . It should make no difference at all but it seems like it might ( my FEO wasn't sure apparently its what they have set up on their system ) Not being a ass about things other than the fact this is all a total waste of taxpayers money , there is no tangible extra risk to the public in someone having a 22-250 or a 22 hornet. When we get into the serious stuff like Elephant guns , 50 BMG etc i get it but still these could just sit in their own class

 

[kenbro]

I would call your Firearms Licensing team to be on the safe side, mine came back with 5.56×45 on . When contacted they said it covered 223 .
Just to be clear , UK rifles comply with CIP and as such .223 and 5.56 NATO operate as the same max pressures.

Kb.