Check out this article. It might help explain the difference a little.
This is a discussion on .223 within the Defensive Rifles & Shotgun Discussion forums, part of the Related Topics category; I have a Mini-14 (approx 6 yrs. old) that I unfortunately haven't fired much, only about 200 rds. of 223. I tend to spend what ...
I have a Mini-14 (approx 6 yrs. old) that I unfortunately haven't fired much, only about 200 rds. of 223. I tend to spend what time I have to practice on handguns. I read in here that the 223 and 5.56 are not the same round. This was news to me, so I read the owner's manual to make sure I could fire 556 out of my rifle. What it does not tell you is which one is more accurate/or preferable for that particular rifle. Anyone have any experience with the two? And was there ever a time or model that did not handle both?
I was told that 5.56 Nato is loaded to slightly higher pressures than .223 Remington, therefore you cannot fire 5.56 in a rifle marked .223.
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The Ruger Mini-14 is chambered for the hotter 5.56 and can safely handle either .223 or 5.56.
If you wanted to wring the maximum possible accuracy out of your Ruger shooting .223 - you would need to have a gunsmith set the barrel back and recut the barrel chamber for shooting .223 only.
Personally I wouldn't bother.
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from what I understand a gun chambered in 5.56 can shoot .223, but a gun chambered in .223 cannot fire a 5.56 (but I could be wrong)