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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.

(post is archived)

[–] • 6 pts

You can shoot what the barrel says you can shoot. A 5.56 caliber barrel will shoot both rounds, but a 223 barrel will only shoot 223. This is because 5.56 has more pressure and can damage a 223 barrel, but not the other way around.

[–] • 4 pts

A .223 barrel can shoot 5.56... once. Disclaimer: Do not shoot 5.56 out of a .223 barrel.

[–] • 1 pt (edited )

https://www.youtube.com/watch?v=UU9O1OimCpE

https://bulkmunitions.com/5-56-vs-223-ammo-19-things-you-need-to-know/

https://exclusive.multibriefs.com/content/the-dangers-of-mixing-up-5.56x45mm-nato-and-.223-remington-rounds/recreation-leisure

Personally, I purchase the least expensive 5.56 ammo available that has good quality, reloadable, brass. I was buying Lake City M855 seconds in loose 2,000 round boxes and never had any problems of any kind with any of them. I burn that up in training and then reload the spent brass as a kind of "Mk318 mod 0 clone" using Hogdons CFE 223 and 62 grain Barnes TSX

https://www.hodgdonreloading.com/hodgdon/hodgdon-cfe-223

https://www.barnesbullets.com/product/tsx/?attribute_pa_bullet-diameter=0-224&attribute_pa_bullet-weight-gr=62&attribute_pa_bullet-type=tsx-bt&attribute_pa_rounds-per-box=50

On south Texas feral hogs it's not a "death ray", but it will do until the death ray gets here.

[–] • 0 pt (edited )

Correct answer goes to glock20!

As for which you should buy/when to use which, whatever .223 is cheapest for practice, 5.56 62gr M855 "green tip" in your SHTF mags because in a long enough barrel they are a match for the type of body armor you might have to worry about from the people most likely to attack you or your house with actual gear on.

[–] • 1 pt

Those M855 green tips aren't very expensive either. I've been getting 20 round boxes for about $14 at my local outdoors store and have been switching them into my mags. Gives me a chance to use the FMJs in there for a little practice, too.

[–] • 2 pts

5.56 has much higher pressure

[–] • 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.

[–] • 1 pt

Mine is also compatible for both but I use 223. No reason, maybe one round is less expensive.

[–] • 1 pt (edited )

5.56 nato barrel can shot both. Lower doesnt matter.

[–] • 0 pt

What about the upper? Is it only the barrel that matters?

This rifle clearly started its life as a Colt AR-15 in 223 caliber. Barrel was swapped out for a 5.56.

[–] • 1 pt (edited )

Lower doesn't matter. 5.56 barrel can shoot both .223 and 5.56.

Get Hornady TAP2 75 gr 5.56 if you can find it.

5.56 has more energy and velocity than .223 in the same bullet weight.

[–] • 0 pt

There's slight difference in head space. A .223 Wylde is for shooting both rounds.

[–] • 1 pt

They're sometimes interchangeable in one direction but I forget which. If you have a .223 gun with a 5.56 barrel you should go with what the firing mechanism and chamber is designed around. That's the actual gun.