F22_RaptoR
CGN Ultra frequent flyer
- Location
- Edmonton, Alberta
From discussions I've had with the gunsmith at Vault Distribution (the official Canadian importer), all of the Canadian market .223 rifles (RDB and SU-16) are marked and chambered for .223 Remington. It's a US Export thing, and the gunsmith told me that the customer service reps at Kel-Tec unfortunately pass on incorrect information that they are 'the same barrels with different markings'. He was very clear that the Canadian market barrels have .223 chambers.
Here's the thing. There IS no difference in the chamber dimensions between .223 and 5.56, except the "lead in" to the rifling is longer in 5.56. Not an issue. If you're reloading using a case that has been full length resized the case will free spin in the chamber. If you are running really hot reloaded ammo (which would be higher than 5.56 Nato anyways) you probably need a longer lead in if you're having high pressure issues. But this is for reloading purposes, not factory loaded ammo. EVERY single European gun is designed to handle the full pressure 5.56 Nato ammo (they do not differentiate between 5.56 and .223 so they treat them as interchangeable cartridges). For American guns, the only time I've had a manufacturer tell me not to use 5.56 in a .223 gun; are bolt action rifles with tight match chambers, as this can cause overpressure issues.
SAAMI specifications. There is a minimum radius requirement on 5.56 cases to handle the higher pressure (NOTE this is only for the brass case, not the chamber itself). You can open both the images up and flip back and forth between them.
.223 Remington
5.56x45mm Nato
This is a comparison of the differences in the case.


















































