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george223
12-14-2011, 7:01 PM
I'm confused now. Up until recently, I always thought that .223 & 5.56 NATO were the same. A few months ago, when I was looking for a 16" barrel for my new AR, I was given a choice to have it chambered in .223 or 5.56. I chose 5.56 because I heard that it is ok to shoot .223 but is not advisable to shoot 5.56 in a barrel chambered for .223. OK now.

I'm looking into reloading again. It has been a long time so I've been scouring the web to refresh my memory. So today I came across a site that lists (diagrams) the specs for numerous rifle cartridges. When I compared Remington .223 & 5.56 NATO, they had the same dimensions. Everything was the same, even the shoulder angle.

So now I'm really confused. What is the difference?

0331Marine
12-14-2011, 7:05 PM
http://www.ar15armory.com/forums/556-223-Ammunition-Ch-t22582.html

gatesbox
12-14-2011, 7:07 PM
Has to do with cartridge tolerances, in many cases the rounds may be identical but 5.56 is rated by SAAMI for higher pressure threshold. Geometrically you are correct the cases are or may be the same dimensions.

Fjold
12-14-2011, 7:39 PM
The chamber in your rifle determines how it handles the higher pressure 5.56 rounds.

http://img.photobucket.com/albums/v214/Fjold/Chamber.jpg

george223
12-14-2011, 8:47 PM
Thanks for teaching me something today. I thought I was going to have to buy some reloading dies for 5.56 but was not able to find any. Already have some .223 dies. So things worked out.

TwoAsoapbox
12-14-2011, 9:11 PM
Headspace mostly. Good posts by others too.

CS Sports
12-14-2011, 9:47 PM
Headspace mostly. Good posts by others too.

Nope. Headspace is exactly the same. The differences were explained above.

paratroop
12-14-2011, 10:05 PM
with 5.56 barrels, they put evil bayonet lugs on them.



just joking around. there are some interesting comments around here today.

UP2MTNS
12-14-2011, 10:33 PM
so, newbie question here....I just bought my first 'new to me' (slightly used) AR-15....RRA upper, specifically, the CAR A4 upper, which, according to RRA is "5.56mm NATO Chambered for 5.56 & .223 Cal" (quoted verbatim from their website)

so do I have a 5.56 barrel or a .223 barrel?

Thanks!

roushstage2
12-14-2011, 10:46 PM
Sounds like they just mean it's a 5.56 that can shoot both 5.56 and .223.

bubbapug1
12-14-2011, 10:48 PM
spelling is the biggest difference

bomb_on_bus
12-14-2011, 10:49 PM
There should be a sticky on this as this question is asked at least once a month!

m03
12-14-2011, 10:56 PM
5.337 :D

FatalKitty
12-14-2011, 11:15 PM
do you realize that you can punch that EXACT subject line into google images and get immediate and perfect information?

luckystrike
12-14-2011, 11:18 PM
I have noticed 556 has a slight bit more "pop" to it. Either way I wouldn't care if the zombies came around tomorrow

Seeker
12-15-2011, 5:12 AM
5.56mm pushes the projectile at about 5,000 more psi than .223.

Mail Clerk
12-15-2011, 7:12 AM
I'm confused now. Up until recently, I always thought that .223 & 5.56 NATO were the same. A few months ago, when I was looking for a 16" barrel for my new AR, I was given a choice to have it chambered in .223 or 5.56. I chose 5.56 because I heard that it is ok to shoot .223 but is not advisable to shoot 5.56 in a barrel chambered for .223. OK now.

I'm looking into reloading again. It has been a long time so I've been scouring the web to refresh my memory. So today I came across a site that lists (diagrams) the specs for numerous rifle cartridges. When I compared Remington .223 & 5.56 NATO, they had the same dimensions. Everything was the same, even the shoulder angle.

So now I'm really confused. What is the difference?

george223,

If you have the 5.56 chambering then your ok to shoot the 223 Remington bullet. You can shoot the 223 in the 5.56 chamber BUT no the other way around. It's just not good.

I don't know much about the whole thing but I do know that basically there are actually 3 chamberings...... 223 Remington, 223 Wylde and the 5.56 Nato
For safety purposes like I said about you can shoot 223 Remington in the 5.56 Nato chamber but not the other way around. If your not sure in the future you can choose the 223 Wylde chambering and it's safe to shoot 5.56 Nato in that chambering. This is because your spliting the difference in the chamberings and the "Wylde" still not the exact same chamber as the 5.56 it is considered to be safe enough to allow enough support so there should not be any catastrophy. The other issue is basically the 5.56 Nato is a hotter cartridge compared to the 223 Remington.

If I'm inccorrect about this then please anyone re-educate me. I'm willing to learn.

Mail Clerk

-hanko
12-15-2011, 7:58 AM
do you realize that you can punch that EXACT subject line into google images and get immediate and perfect information?
Back to reality...this is calguns.net. No one googles. Ever.;)

-hanko

akjunkie
12-15-2011, 8:00 AM
The AMMO ORACLE should be Mandatory Reading for all AR enthusiast.

http://ammo.ar15.com/ammo/project/hist_diff.html

SoCalSig1911
12-15-2011, 8:56 AM
do you realize that you can punch that EXACT subject line into google images and get immediate and perfect information?

That's why I've never asked :D Google=Answers.

rp55
12-15-2011, 11:37 AM
Here ya go. This is pretty much the same info that Fjold posted but in a (for me) more understandable illustration.
http://i83.photobucket.com/albums/j302/rpwhite55/guns/223v556.jpg

xrMike
12-15-2011, 1:11 PM
Don't forget it works the opposite way with .308 < > 7.62 :D