If you’re a first time AR15 owner, you may not be well versed in which ammunition to use, due to common misconceptions that are sometimes used to dismiss any concern of over-pressure in chambers when the wrong one for the .223 chambering is used.
Without going into the specifications right away, the 5.56NATO round produces 58,000 pounds of pressure per square inch while the .223 produces 55,000. Additionally the 5.56 round’s throat is .125” longer than the .223’s.
“So what”, you ask?
Here’s the ‘what’ of it:
If you’re shooting your .223 from a 5.56NATO chambered platform you may run the risk of lower than optimum performance of the .223 because of the .223’s inability to reach is optimum pressure of 55K PSI in the larger 5.56NATO chamber. It will be, ‘ok’ but if you’re trying it out of, say, an AR pistol with a barrel shorter than 14.5…
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