The 5.56x45mm NATO is the military version of the .223 Remington, which is one of the most widely used centerfire cartridges today. Starline’s 5.56x45mm brass is identical to Starline’s .223 Remington brass except for a slight change in the metallurgy making it harder at the base of the case.
When loaded at .223 Remington pressures, Starline's .223 brass is safe to use in any firearm chambered for .223 or 5.56x45mm. If loaded to 5.56 pressures, you need to use firearms labeled for use with 5.56mm. It can be unsafe to fire 5.56mm ammunition in firearms with a .223 Remington chamber.
**WARNING** In firearms that use a floating firing pin (such as the AR-15 and its variants), dropping the bolt on a chambered round could lead to a slam fire. It is important that these firearms are loaded from the magazine so that the bolt loses inertia when it strips a round from the magazine. It is also important NOT to use sensitive primers that aren’t designed for use in an AR, as this increases the chance of a slam fire.
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* Starline Brass does not sell any loaded ammunition. What you are purchasing are brass cases only and will need to be loaded into ammunition in order to be fired from a firearm.
