Always Keep Your Powder Dry! The Art & Science Behind The Shot.

Differences Between the 223 Caliber and 5.56 Caliber.

There has been a lot of question and confusion about the 223 cal and 5.56 cal. Many have asked me, "Jim, are they the same?" and "Are they interchangeable?"

The answer is YES they are, but in some guns.

The outside dimensions of the cartridge are exactly the same! But the inside dimensions are not.

The 5.56 is the military loading for the round. It develops a faster and slightly harder hitting projectile. It also develops 20,000 psi more chamber pressure, which results in more stretching and expanding of the case as the bullet leaves it. The 5.56 case is thicker than the 223 to accommodate for the stretching, (better known as fire forming). Again, the outside dimensions are the same but the inside dimensions are not.

The 223 and 5.56 are interchangeable in all AR platforms and military style rifles. The reason is that these style rifles are reamed out at the feed ramp, throat and chamber. This is done for reliable function in combat or rapid fire. When it comes to bolt actions this is not the case! Bolt actions are designed for accuracy, and therefore require much tighter machining and tolerances.

You wouldn't see bolt actions chambered for 5.56; they are chambered for 223. If a 5.56 is loaded and fired from a bolt action in 223 the result can be a jam, or in some cases (as it has been known to do), the extractor claw can wear or break off. So the rules are simple!