Shooting .223 in 5.56 chamber

[BREATHER]

I understand that you can shoot .223 out of a 5.56 chamber. BUT do you have to change to a mag that is for .223.... or can you use the same mag...???

[patrick0685]

Same mag same everything

[DeusExMachina]

The ammo is, for all intents and purposes, the same. They are rated slightly different and usually 5.56 has thicker brass. The chamber is where the important differences lie.

[BPTactical]

Your good to go shooting 223 in a 5.56 chambered barrel, however if the barrel is marked .223 you want to be leery of shooting 5.56 through it. 5.56 is loaded to higher pressures and a 223 chamber is a smidge tighter, especially in the throat.

[BREATHER]

Thanks, Guys. My M-4 is marked 5.56....Good to go ,,, gotta get out to shoot it.....

[gcrookston]

No problems shooting .223 out of 5.56. However, occasionally one might come across a .223 that really, really, doesn't like 5.56

Cases on the left: 5.56.... shot out of a Bushmaster 'high bred' chamber that was, in fact, .223...

[legaleagle]

FWIW - the dies to reload each are the same. I have never seen a 5.556 die set, it always .223/5.556.

[BPTactical]

FWIW - the dies to reload each are the same. I have never seen a 5.556 die set, it always .223/5.556.

Dimensionally they are virtually the same. The 5.56 has a slightly looser chamber but the biggest difference is the throat or "leade" of the chamber. It is a touch longer on a 5.56. The looser chamber and longer leade are part of the military aspect of the 5.56, the chamber for reliability and the lead for gov contract ammo that may have a wide tolerance range.
When you stuff a 5.56 round in a .223 chamber you can actually "crowd" the round into the rifling, causing a pressure spike.

[NukeRJ]

Dimensionally they are virtually the same. The 5.56 has a slightly looser chamber but the biggest difference is the throat or "leade" of the chamber. It is a touch longer on a 5.56. The looser chamber and longer leade are part of the military aspect of the 5.56, the chamber for reliability and the lead for gov contract ammo that may have a wide tolerance range.
When you stuff a 5.56 round in a .223 chamber you can actually "crowd" the round into the rifling, causing a pressure spike.

Partially correct...
The chamber is slightly oversized for variance in chrome lining and expansion during extended use- i.e. fa heat build up. The throat is longer for reduced pressure created from the slightly smaller case capacity of the 5.56 casing, as well as the thickness of the neck brass is also increased to prevent folding of the case during ejection in a hot chamber- the case head is thicker to prevent separation in hot chambers. And mil-spec ammo is actually held to higher standards than commercial ammo.

If you are wondering where this information comes from, my team was one of several selected for the field trials when USASOC was testing the SCAR platform for future deployment.

[Hkguy45]

how'd the SCAR work out?