is the pressure difference between .223 / 5.56

a big deal?

I see some places that say the pressure difference (55k vs 60k) is no big deal then some places say you should never put 5.56 x 45 (5.56NATO) through a weapon chambered for .223

what's y'alls opinion (or the ground truth)?

You could write two books on the subject, but my hard and fast rule is this. In the 5.56 and .223 Wylde guns, I run whatever. In .223 chambered guns, shoot only .223. The 223 has a shorter throat, that with increased pressure loads, could be too much. Maybe would be ok, but I really don't want a rifle coming apart next to my face. The Wylde chamber supposedly gives you the best of both worlds, ability to use whatever ammo with "theoretical" increased accuracy.

My opinion and take it for what you will. There ain't enough difference to matter. Don't do it now because I shoot my on reloads, but I have shot 5.56 in a .223 marked rifle and no issues. Taken to an extreme with high pressure 5.56 shot in a weak chambered .223 there might could be an issue. I have bought .223 that measured exactly the same as some once fired .mil brass. Held exactly the same amount of water too. Maybe years ago there was a bigger difference I don't know.

I'm following. safety first, but some folks "chicken little" over the slightest thing.

I have the M4 so I can use either round...but I see some .223 chambered AR-15s that are decent priced, but I would like to just use the ammo I already have (which is mostly 5.56)

PLUS someone listed the green tip stuff on here and I missed it...it was gone in like an hour!

Get you one and a .223 Wylde barrel, I'll swap it out for you. I built kind of a SPR gun with a 18" criterion HBAR in .223 Wylde. It's plenty accurate for an autoloader. If I want more I grab the bolt .22-250.

From what I have gathered, case dimensions are going to be identical, it's just the chamber they are fired in. I seem to recall the LC brass being heavier and with less case capacity due to the web of the case being thicker. The thought being that most of the ammo is going in full auto guns with slightly larger chamber body dimensions to cut down failure to feed/eject, and the thicker brass equaled less ruptured cases, head separations, etc.

THE situation in all that is with surplus/military ammo the 5.56 brass is thicker than .223 and therefore holds less powder/creates more pressure. If you load 5.56 cases this is particularly important.

Rifles don't blow up with one hot round. Repeated firing of high pressure rounds will stress the steel until it eventually fails.

^^^^^^^^^

In addition to the excellent info already given when the .223 remington was created (1957) there was no 5.56mm round. In 1980, the .223 Remington was transformed into a new cartridge, a 62-gr full metal jacket bullet with a 7-gr steel core for better penetration and designated 5.56×45mm NATO (SS109 or M855).

That's why on some old rifles like Colt ar15, it say 223 but is acceptable to fire 556. Or so I've been told.

I haven’t seen any currently produced AR labeled 223 only. Either 223 Wylde or 556.

Just go by the book. who cares? work a load up safely that performs for you. a few extra FPS don't matter, only the hits in the 10 ring


BOOM