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Rockhound
10-15-2009, 12:45 PM
I'm just building my first AR. I have a lot of .223 ammo. If I buy a 5.56 NATO upper, can I fire the .223 and if I can will there be any issues?

Thanks for any help

johnrunner89
10-15-2009, 12:48 PM
Very common question. If the AR-15 is for a 5.56 (Get an upper and lower that is chambered for 5.56 and you should be fine) than both .223 and 5.56 NATO will work.

HappyG
10-15-2009, 12:48 PM
Generally, if it's a 5.56 marked rifle, it can fire both 5.56 and .223 If it is a .223 marked rifled, only fire .223 and not 5.56 as the pressure in the cartridge may be too high and dangerous.

CFV
10-15-2009, 12:58 PM
Is accuracy comprimised.... say between a 5.56 and a .223 barrel... the .223 would be more accurate with the .223 barrel

reidnez
10-15-2009, 1:02 PM
Is accuracy comprimised.... say between a 5.56 and a .223 barrel... the .223 would be more accurate with the .223 barrel

Very marginally, perhaps (5.56 chamber specs are slightly more generous than .223 for reliability). You really wouldn't see a difference unless you were using all-match components, and match ammunition.

Get a 5.56-chambered upper and you are good-to-go. It's really that simple.

reidnez
10-15-2009, 1:05 PM
Very common question. If the AR-15 is for a 5.56 (Get an upper and lower that is chambered for 5.56 and you should be fine) than both .223 and 5.56 NATO will work.

Just a clarification, lowers aren't "chambered" in anything. The only limiting factor is the size of the magazine well. Other than that, you can find uppers in a huge range of calibers which work with a standard lower.

johnrunner89
10-15-2009, 1:06 PM
Just a clarification, lowers aren't "chambered" in anything. The only limiting factor is the size of the magazine well. Other than that, you can find uppers in a huge range of calibers which work with a standard lower.

Yea I saw I typed that after I posted it, I meant to say the lower marked as 5.56 but even than a .223 lower should do fine.

johnrunner89
10-15-2009, 1:07 PM
Yea I saw I typed that after I posted it, I meant to say the lower marked as 5.56 but even than a .223 lower should do fine.

reidnez
10-15-2009, 1:10 PM
Yea I saw I typed that after I posted it, I meant to say the lower marked as 5.56 but even than a .223 lower should do fine.

Assuming it's an AR15 lower and not an AR10, it doesn't matter what the marking says. Lots of lowers are simply marked "multi." Heck, you could have a custom lower that says "35mm" on it. Doesn't matter.

Rockhound
10-15-2009, 1:15 PM
Thanks, this all really helps. I get my lower in nine more days and will post some pics after the AR is built.

So far I have CMMG lower, Rock River match grade lower kit, and Magpul Mil spec stock. I'm thinking about a Yankee Hill upper. Also like the Mako T-Pod for the front grip.

johnrunner89
10-15-2009, 1:44 PM
Assuming it's an AR15 lower and not an AR10, it doesn't matter what the marking says. Lots of lowers are simply marked "multi." Heck, you could have a custom lower that says "35mm" on it. Doesn't matter.

Yup. Nice thing about a standard lower is that you can put so many types of uppers on them.