Is 223 and 5.56 the same?


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sparkyguy
March 12, 2008, 03:56 PM
I'm ignorant in this subject, forgive me. I picked up some range brass and some said 223 and others had 5.56. My question is, are they the same? Can I mix the brass and load them equally?

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LexDiamonds
March 12, 2008, 04:12 PM
They are the same outer dimensions, but the 5.56 brass tends to have thicker walls, thus lower internal capacity, thus increased pressure for any equal load compared to .223 brass.

This is a broad generalization and as always, you should work up loads carefully.

shooter762
March 12, 2008, 05:38 PM
All you want to know and more here :)

http://ammo.ar15.com/

Shooter762.

strat81
March 12, 2008, 05:46 PM
They are the same outer dimensions, but the 5.56 brass tends to have thicker walls, thus lower internal capacity, thus increased pressure for any equal load compared to .223 brass.

Correct. The other issue is that 5.56 and .223 are also different chambers, the 5.56 being a bit more generous.

Shooter762's link will explain it all, and then some.

W.E.G.
March 12, 2008, 05:58 PM
Rifles chambered in .223 Remington and 5.56 NATO have sufficiently different chambers that 5.56 ammo should not be fired in chambers marked .223 Rem.

http://i227.photobucket.com/albums/dd7/rkba2da/rifle%20pics/AR-15/556-223chambercomparison.gif

rcmodel
March 12, 2008, 07:00 PM
Can I mix the brass and load them equally?For reloading purposes, they are the same, maybe.

Some military 5.56 brass may be heavier, and have less capacity.

However this is not a hard and fast rule in .223/5.56, so much as it is in .308 & 30-06.

I have found some lots of GI 5.56 brass thet weighed less then other lots of comercial .223 brass.

I have several thousand LC69 cases that average within 1.0 grain of being the same weight as some new Remington .223 brass I bought last year.

Regardless, you should probably sort them out by headstamp and work up loads for each, unless it all weighs the same on your powder scales.

If it weighs the same after sizing & trimming, it has the same internal capacity.

rcmodel

ants
March 12, 2008, 07:31 PM
If it worries you, leave the 5.56 on the ground for experience reloaders to safely dispose of it for you. I'm sure they will appreciate it.

There continues to be a large amount of misinformation or misunderstood information in reloading. But I guess it's better to be safe than sorry.

Owens
March 12, 2008, 07:51 PM
Just to add...
One of the main reasons for having a slightly more generous throat/chamber is to ensure extraction of fired cases in auto and 3 round burst.

rcmodel
March 12, 2008, 07:58 PM
And to handle longer tracer bullets.

rcmodel

mallc
March 12, 2008, 09:09 PM
My experience is that .556 is much more likely to have crimped primer pockets.

Scott

alsaqr
March 12, 2008, 09:19 PM
For forty years I have weighed all my cases that are used in rounds made for serious accuracy.

Federal Match and Lapua are the heaviest commercial cases. They are much heavier than US military cases. LC cases are usually a little lighter than US commercial cases.

Some Brit military cases are very heavy and I just chunk them into the brass barrel:

http://www.ar15barrels.com/data/223weights.xls

Contrary to what SAAMI will tell you: There are 10-12 different .223 and 5.56mm chambers. This company chambers about eight of them.

http://ar15barrels.com/data/223-556.pdf

frogomatic
March 12, 2008, 09:22 PM
in dimension, yes. in pressure, no.

a bolt action, breech loader, or slide action will never know the difference between 223R, and 556N.

however,

a semi auto knows the difference. The pressure curve is different between the two loadings. Gas operated semi-autos require a certain pressure, at a certain time, through a certain size gas port to cycle properly. Guns that are designed to operate with a 556N pressure curve (like the ubiquitous AR) don't like to function very well at the 223R pressure curve, and often will have cycling failures. Guns designed for a 223R pressure curve can beat the hell out of themselves when subjected to 556N pressure curves.

Bullet
March 12, 2008, 10:28 PM
You might look here -

http://www.6mmbr.com/223Rem.html


.

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