223 vs. 5.56 Facts and Myths

223 Remington and 5.56 NATO are sorta-kinda the same cartridge, but there are some important distinctions between the two. Problem is, the internet is jam-packed with poor assumptions, dangerous advice from misinformed shooters, and downright false information.

What to do?

Well, you can watch this guy’s video. He calls his channel “gavintoobe,” and he knows what he’s talking about in this video. There may be some errors in his terminology, but I found only one (he referred to the case head as the rim). Otherwise, it’s a well-researched and well-presented discussion of the 223 and the 5.56, their development, their differences, and the way the military measures pressure as compared with the way SAAMI does so.

Just a few key points to pique your interest:

• As a rule, 223 and 5.56 cartridge cases are the same.
• Don’t fire 5.56 in a rifle marked 223 Rem.
• The biggest difference is in the chamber, but not all 5.56 chambers are the same.

There’s a lot more, but you might as well watch the video. He packs a lot of great info in about twelve minutes.

Have more questions after watching? Visit the Ultimate Reloader website to check out Gavin’s writeup.

Russ Chastain

Editor & Contributing Writer Russ Chastain is a lifelong hunter and shooter who has spent his life learning about hunting, shooting, guns, ammunition, gunsmithing, reloading, and bullet casting. He started toting his own gun in the woods at age nine and he's pursued deer with rifles since 1982, so his hunting knowledge has been growing for more than three and a half decades. His desire and ability to share this knowledge with others has also grown, and Russ has been professionally writing and editing original hunting & shooting content since 1998. Russ Chastain has a passion for sharing accurate, honest, interesting hunting & shooting knowledge and stories with people of all skill levels.