For most shooters the difference between .223 Remington and 5.56×45 NATO is minor, but it matters because 5.56 is typically loaded to higher pressures and uses a slightly different chamber leade.

Julia Kagan is a financial/consumer journalist and former senior editor, personal finance, of Investopedia. Lea Uradu, J.D., is a Maryland state registered tax preparer, state-certified notary public, ...