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Thread: quick question about AR 15's

  1. #1
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    quick question about AR 15's

    I know of the fact that the 5.56mm has a higher pressure than the .223

    I just bought.... place in layway a New S&W AR 15 Sport. It was marked to handle both the 5.56 NATO and .223 round. I even checked on the barrel and it had 5.56mm on it. But after I did a few searches online, I have read comments a AR 15 can be "marked" with 5.56mm but not be able to handle the NATO round????

    Is this true... or some people who got their facts wrong?

    I would think or even trust the markings on a weapon... that if it states .45ACP... I would expect to use it rather than Colt or another type of ammo.

    Please, let me know... I have also picked up 420 rounds of 5.56mm... I don't want to be surpised with my fingers flying off or something.

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    I would think if It's marked 5.56 it would shoot either 5.56 or .223. I don't think the good boys at the ATF would let them mark a gun with a caliber that the weapon could not withstand. Now don't try to shoot 5.56 out of a gun marked .223. That's the same as a 38 and a 357.
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    Regular Member 09jisaac's Avatar
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    I have an S&W M&P15T or something (flat top, big front sight) and have put plenty of 5.56 through it, last I tried to figure it it was upwards of 1500.

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    There would be massive liability on the part of the manufacture if they mark it for a particular caliber and it can't handle that caliber.
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    Regular Member 09jisaac's Avatar
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    Quote Originally Posted by Carry24/7 View Post
    I would think if It's marked 5.56 it would shoot either 5.56 or .223. I don't think the good boys at the ATF would let them mark a gun with a caliber that the weapon could not withstand. Now don't try to shoot 5.56 out of a gun marked .223. That's the same as a 38 and a 357.
    That is not the exact same. Most big names in the industry build even their .223 guns to handle the 5.56 because of how close they are. They don't want the guns they produce to blow up, even if it is operator error.

    But they build .38 guns specifically not to accept .357mag rounds because of the difference in max pressure.

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    As others have eluded to, if it's marked 5.56; especially on the barrel, it can shoot both 5.56 and .223. 5.56 generally are chambered with a longer throat length for the heavier military bullets. .223 is generally chambered more tightly and with a shorter throat length. Because of the already higher pressure of the 5.56, if you run it in a .223; the bullet may hit the rifle lands or even set back a little. This causes even higher pressure and the possibility of danger.

    A Wylde chambered .223 has a longer throat to shoot the heavier bullets and I wouldn't personally be worried about 5.56 out of a Wylde .223 chambering.
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    Regular Member HKcarrier's Avatar
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    +1

    If the bbl is marked 5.56 and especially if there are other 5.56 markings on the firearm, it's good for 5.56.
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    I think the OP is looking for personal experience .. I think he can read , he has indicated he understood what the manufacturer has said.

    I, personally, would fire 223's through it -- its what it was designed to fire.

    Enjoy clearing out your jams & enjoy your gun.

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    Quote Originally Posted by davidmcbeth View Post
    I think the OP is looking for personal experience .. I think he can read , he has indicated he understood what the manufacturer has said.

    I, personally, would fire 223's through it -- its what it was designed to fire.

    Enjoy clearing out your jams & enjoy your gun.
    The barrel is marked 5.56. It's chambered for 5.56, it will shoot 5.56 or .223. It doesn't matter what the lower receiver says. I've got one that says caliber "multi". I can't seem to find that round.
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    Regular Member 09jisaac's Avatar
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    If his smith is as good as mine then he won't have to deal with any jams after the 1st 100 or so rounds.

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    Thanks everyone... it is weird... the barrel is marked for "5.56". In about a month I will have it out of layway. We'll see how it performs

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    Quote Originally Posted by Carry24/7 View Post
    ...Now don't try to shoot 5.56 out of a gun marked .223. That's the same as a 38 and a 357.
    Bad analogy. A .357 is on the order of twice the pressure of a .38 and they will not chamber in a properly made firearm of the lesser.

    While the Internet consensus is that you should not fire 5.56mm NATO in ".223 Remington" chambers, the truth is that it happens everyday, and I've yet to actually hear of catastrophic consequences, though I would like to read about them if anyone has some knowledge of actual damages.

    The 5.56mm chamber has a longer leade designed to take advantage of some of the special military ammo that requires it. The popular M855 62-gr and M193 55-gr ammo is not among them. But the thicker military brass will still lead to higher pressures than the normal stuff. This is more like hot handloads (if that) than using magnum proof loads.
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    Campaign Veteran deepdiver's Avatar
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    Quote Originally Posted by Firedawg314 View Post
    I know of the fact that the 5.56mm has a higher pressure than the .223

    I just bought.... place in layway a New S&W AR 15 Sport. It was marked to handle both the 5.56 NATO and .223 round. I even checked on the barrel and it had 5.56mm on it. But after I did a few searches online, I have read comments a AR 15 can be "marked" with 5.56mm but not be able to handle the NATO round????

    Is this true... or some people who got their facts wrong?

    I would think or even trust the markings on a weapon... that if it states .45ACP... I would expect to use it rather than Colt or another type of ammo.

    Please, let me know... I have also picked up 420 rounds of 5.56mm... I don't want to be surpised with my fingers flying off or something.
    A reputable manufacturer is not going to put a. 223 barrelled upper on a lower marked 5.56 just for liability reasons if nothing else, but some guy in his garage someplace will. As many people have alluded to above, it is the caliber marking on the barrel that matters for safety on this issue. I have seen presumably homebuilt ARs with a lower marked 5.56 and a barrel marked. 223, so yes, it can/does happpen. I have read that while a. 223 lower doesn't have a safety issue with 5.56 as long as the upper is 5.56, it can have practical issues with certain 5.56 rounds. I've been advised more than once by people who know far more about these rifles than I ever will to always check both barrel and lower caliber markings before using 5.56 ammo.

    So it sounds like you are a good to go with a factory marked 5.56 lower and barrel. I wouldn't be worried about it any more.

  14. #14
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    Just for clarification, there is absolutely no physical difference in the lower receiver between .223/5.56 except for the marking of .223/5.56 on the side.

    On the upper receivers, M4 style differs in that it has extended feed ramps. There is a difference in the M4 barrel extension as well. Neither of these things matter for .223 vs. 5.56 though.
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