5.56 in 223

Technically there's a difference in throat length (the bullet in a 5.56 chamber has more travel before engaging rifling). I've shot plenty of 5.56 out of 223 bolt guns and never had an issue.
It's up to you but in billions of rounds of 223 and 5.56 being shot I've never heard of anyone who's heard of anyone who's had an issue...

5.56 NATO/Milspec is loaded hotter, chambers are slightly different. Don't trust all guns to be able to handle the differences.

Do a little research and decide if the benefit outweighs any perceived downside.
You don't say how many is "quite a few"...

Or, if you have any doubt, you could save the ammo for your AR or other 5.56/Wylde-chambered guns.


[obligatory Wylde chamber reamer reference]

Send it. In the real world you'll never have an issue with a bolt gun. People have used them interchangeably for decades before the internet told us not to.

The only issues anyone has ever heard of is shooting 5.56 in a semi-auto with a 223 chamber. The extra pressure MIGHT result in unreliable cycling and if done long term premature parts wear. The only semi-auto I can ever recall are the very early Ruger Mini-14's. They quickly went to a 5.56 chamber.

Are you sure your Ruger American is a 223? I thought they had 5.56 chambers.

I wouldn't worry too much about it. I've fired 5.56 in several 223 chambers and the worst that happened is the bolt lift was a little heavier.

I think it`s probably more of a matter of what you feel comfortable doing. My rifles have " .223 Rem " stamped on their barrels. So, I choose to shoot .223 only. Could I shoot 5.56? In all probability yes. Would I have a little nagging concern in the back of my mind? Probably. I go shooting to relax, not worry, even slightly if I can help it. .223 ammo is plentiful also, so....

If the brass doesn't look overpressured and the primers aren't pierced you are probably okay. Some 223 rifles are chambered different so may show more preasure signs than others. In general 5.56 nato should be used in 5.56 chambers because of more freebore. If you load the 223 near max pressure and seat bullets too close to the lands you will see overpressure signs similar to using 556 ammo with shorter OAL in it. You may be surprized to find out that some factory ammo labeled as 556 is not loaded to max pressure - I've clocked some 556 at slower fps than 223 but the powder burn speed and not pressure could be at play also.

You may enjoy this article.

5.56 vs .223: What’s the Real Difference Between These Popular Cartridges?​

I had a 223 Bushmaster AR15 duty gun. There was a summer that we ran mostly 5.56 in training due to supply issues. When the Bushmastets got hot we would start to get popped primers. Not every round. But it jammed up several guns each training day with primers getting into the action and trigger group. I have never heard of any actual damage to the guns that I can remember.

Ask Ruger? Is this the one with the 22" barrel that takes AR magazines? I've looked into those a time or two just never laid out the cash.

C-grunt said:

I had a 223 Bushmaster AR15 duty gun. There was a summer that we ran mostly 5.56 in training due to supply issues. When the Bushmastets got hot we would start to get popped primers. Not every round. But it jammed up several guns each training day with primers getting into the action and trigger group. I have never heard of any actual damage to the guns that I can remember.

Click to expand...

Thank you providing insight on your real-world experience.

I tend to think of this question mostly in terms of bolt guns, but I guess it could apply to a semi also. At least theoretically.

Better info than probably many of us can provide - who may possibly just be speaking mostly hypothetically.


I will admit it hasn't come up a lot for me personally. I will also admit that I am not particularly worried about the commercial .223 bolt guns I own as far as this issue. If I was shooting a match-grade gun, I might give it a bit more thought and concern.

I have a CZ 527 chambered in 223 and fire 5.56 no problem. You can get away with the difference in a bolt gun.

ask Ruger. is it stamped? ".223 Remington" means one thing, and ".223 Caliber" means another.