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I have both 223 and 5.56 rounds on hand, pic related. My AR's lower says .223 caliber, but it has a 5.56 NATO barrel on it. I assume due to the barrel it's safe to shoot the 5.56, but what about the 223?

Before thinking about it much I've shot both through it, and nothing went wrong. Well, yet. After thinking about it I'd rather get some second opinions before chancing it again.

Internet literature and video research turned up inconclusive results, at least from what I found.

I have both 223 and 5.56 rounds on hand, pic related. My AR's lower says .223 caliber, but it has a 5.56 NATO barrel on it. I assume due to the barrel it's safe to shoot the 5.56, but what about the 223? Before thinking about it much I've shot both through it, and nothing went wrong. Well, yet. After thinking about it I'd rather get some second opinions before chancing it again. Internet literature and video research turned up inconclusive results, at least from what I found.

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[–] • 1 pt

If the lower says .223 than that's all I would fire through it. 99.9% chance no damage will come from the 5.56 but why risk it. .223 is usually cheaper anyway. At some point I'd switch to make the barrel and lower compatible.

[–] • 2 pts

Bro bro ALL LOWERS ARE EXATCLY THE SAME. Its the barrel that matters.

[–] • 0 pt

You're almost certainly correc. I don't think I've ever seen an AR lower marked .223, maybe its really old or some chinese shit. If it's marked .223, I'd assume there was a reason. Maybe the manufacturer is a dumbass and that's the reason. Do you really want to be using a gun part manufactured by a dumbass in a way they didn't intend?

[–] • 0 pt

Wrong. Don't listen to this person for advice about guns.

The lower makes no difference in 5.56 vs .223. The barrel is what matters. 5.56 can shoot both.

[–] • 1 pt (edited )

You know nothing about OP's gun. All you know is that he's fired at least one round .223 and 5.56 through it and the lower is marked .223. Have you seen a lower marked .223. I haven't. Are you sure it's an AR? How do you know? The advice of just shoot whatever through that bolt action .223 hunting rifle that your buddy sold you for $50 while calling it and "AR" is not exactly sound. Why does it have a 5.56 barrel? Who put it on?

I advocated for and abundance of caution. Sorry if you feel that's wrong, but I've seen plenty of people refer to something as an AR that clearly wasn't. I don't know why the manufacturer marked his lower as .223 and neither do you. When in doubt, follow the manufacturer guidance. OP is clearly in doubt.

[–] • 0 pt (edited )

Don't give people advice about guns if you aren't informed. I happen to be extremely informed about AR-15s and gunsmithing.

The .223 marked lower is an AR-15 pattern lower. They are all the same.

Yes, there are AR lowers marked .223. Colt makes them for one.

Again, .223 being marked on the lower doesn't matter.

The upper matters. You don't want to shoot 5.56 through a barrel/chamber marked .223 because 5.56 has higher case pressure. Shooting .223 through a 5.56 barrel is fine.