223 vs 5.56

[Sas874runner]

So the 223 and 5, 56 cartridges are the same dimensions. So from what I can understand they are the same round. The only difference is the 5.56 twist is way to fast for any bullet smaller than 62 gr. Is the a correct assesment or is there other differences?

 

[Ridge_Runner]

nope, the 5.56 is rated by saami at a bit more pressure, and has a longer leade than the 223, so if you fire a 5.56 in a 223 chamber, the pressure runs much higher, and some claim it is unsafe, some claim not. I don't do it.
RR

 

[Guy Miner]

Well, the military had the 5.56 long before they adopted the heavier bullets & faster twist...

Link to an excellent article on the .223, including an explanation of the differences between the .223 and 5.56 cartridges:

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

Interesting stuff.

Guy

 

[Sas874runner]

Ok. So what about loading with 223 lake city brass. Which I believe is a military brass? Correct?

 

[onesonek]

I load LC brass. I have never weighed it, so I can't say how it varies from the Rem. or Win..
But I do notice, it tends to hit max charge weight, a bit quicker than the other two. With that I'm guessing it slightly heavier ot thicker. That small capacity, it don't take much.

 

[RiverRider]

LC brass would be 5.56 brass, actually...but it does not matter one bit. It is no more different from commercial .223 brass than Winchester .223 brass is different from Remington .223 brass. As far as capacity variations go, LC brass in my experience is practically the same as all the rest of the commercial .223 brass. When I had three batches of brass on hand I figured out the average weights:

FC 96.1 grains
LC92 91.2 grains
Winchester 92.3 grains

Notice that the LC brass was the lightest. I did not measure case capacity at that time, but I'd be willing to bet a dollar to a donut that the LC capacity was [probably greater than the others.

I have found the opposite to be true when comparing commercial .308 to LC 7.62 brass.

 

[Sas874runner]

So my ar is stamped for 223 and 556. But a friend of mine has a colt 556. Can you load 223 cases to fire and cycle reliably out of a 556 ar? I just bought 3000 cases for 223 and he can't get rounds for his 556.

 

[runtohunt]

You can shoot 223 through an AR labeled as 5.56. As was stated before, 5.56 is loaded to higher pressures. My AR labeled as 5.56 shoots 223 without a hiccup. But, I would not shoot factory loaded 5.56 through my varmint AR labeled as 223. Building your own loads using 5.56 brass would be a different story.

 

[hunting1]

I use mixxed brass or LC, Rem, Win, Fed, etc and no issues, just don't load them to the hill. 25 grs of H335 and 55 gr of choice is like PB&J, Ebony and Ivory, Obama killing the economy, etc.

 

[Sas874runner]

So if I was to load some brass with say a 68 grain bullet it should hold together and fire well through his 1:7 twist.