.223 Rem vs. 5.56x45mm NATO — What You Need to Know « Daily Bulletin
Probably the most popular centerfire rifle round in the Western Hemisphere is the .223 Remington and its metric match, the 5.56x45mm. Though many folks use .223 Rem and 5.56x45 interchangeably, there are some meaningful differences in specifications for the original .223 Rem and the 5.56x45mm...
