So it’s the firearm, not the round?
Yes, I’ve loaded a bunch of 5.56 and .223 brass. There is no more variation between the two than there is normal variation between different brands of brass.
On a .223 Remington spec rifle, the leade will be 0.085”. This is the standard described by the Sporting Arms and Ammunition Manufacturers’ Institute, Inc. (SAAMI). The leade in a 5.56 NATO spec rifle is 0.162”, or almost double the leade of the .223 rifle.
A shorter leade in a SAAMI spec rifle creates a situation where the bullet in a 5.56 NATO round, when chambered, can contact the rifling prior to being fired. By having contact with the rifling prematurely (at the moment of firing), chamber pressure can be dramatically increased, creating the danger of a ruptured case or other cartridge/gun failure.
I copied and pasted that, as it explains the situation better than I can. The leade is the amount of distance the bullet has to jump before encountering the rifling. If you have the bullet jammed against the rifling, pressure will go up, makes sense. Also, if the bullet is seated farther out (less bullet in the case) it has the same effect as increasing the capacity of the case, which also makes common sense. The more room in the case with the same powder charge, the lower the pressure and vice versa.
Technically, it is the chamber that is at variance, not the ammo, in a general sense. 5.56 ammo may be loaded hotter, due to the fact that it is made for rifles with more leade (throat), so may be too hot in a .223 chamber. That said, I can’t recall anyone ever getting hurt by 5.56 in a .223 either.
Yes, I’ve loaded a bunch of 5.56 and .223 brass. There is no more variation between the two than there is normal variation between different brands of brass.
On a .223 Remington spec rifle, the leade will be 0.085”. This is the standard described by the Sporting Arms and Ammunition Manufacturers’ Institute, Inc. (SAAMI). The leade in a 5.56 NATO spec rifle is 0.162”, or almost double the leade of the .223 rifle.
A shorter leade in a SAAMI spec rifle creates a situation where the bullet in a 5.56 NATO round, when chambered, can contact the rifling prior to being fired. By having contact with the rifling prematurely (at the moment of firing), chamber pressure can be dramatically increased, creating the danger of a ruptured case or other cartridge/gun failure.
I copied and pasted that, as it explains the situation better than I can. The leade is the amount of distance the bullet has to jump before encountering the rifling. If you have the bullet jammed against the rifling, pressure will go up, makes sense. Also, if the bullet is seated farther out (less bullet in the case) it has the same effect as increasing the capacity of the case, which also makes common sense. The more room in the case with the same powder charge, the lower the pressure and vice versa.
Technically, it is the chamber that is at variance, not the ammo, in a general sense. 5.56 ammo may be loaded hotter, due to the fact that it is made for rifles with more leade (throat), so may be too hot in a .223 chamber. That said, I can’t recall anyone ever getting hurt by 5.56 in a .223 either.