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5.56 and .223 compatibility?

DONDALINGER
If I have a 5.56X45 upper, can I shoot .223 through it without any damage or poor accuracy? I heard you should not shoot 5.56 ammo if the bore is designated .223, but the 5.56 will shoot both.

Is this correct?

Thanks, Don
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Comments

11 comments

Date Votes
  • Pistollero1050
    Yes, no damage will occur. accuracy will not be affected. going the other way is not possible.
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  • Justjump
    quote:Originally posted by Pistollero1050
    Yes, no damage will occur. accuracy will not be affected. going the other way is not possible.


    Not to stir a hornet nest or anything but I had always heard this and just never understood it. So 20 minutes ago after seeing this post I put it to the test. I dug up some Lake City M855a1 ball that has been laying around here for a decade or so. I generally try not to shoot anything but pristine ammo in my civi rifles and this ball ammo is old and a bit filthy. Wipe 3 rounds off and slide them in a Rem 700BDL custom deluxe. Guess what 3 in less than 1/2 inch at 100 yds. If I have erred somewhere on my experiment let me know. I'll upload pics as best I can if that is needed. I understand that theory and real world are sometimes not aligned[:)]
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  • sandwarrior
    Yes, you can shoot .223 in a 5.56 chamber.

    However, contrary to what Pistollero1050 says, it is quite possible to shoot 5.56 in a .223. They are the same dimensions and use the same diameter bullets.

    THE REASON YOU SHOULDN'T SHOOT 5.56 IN A .223 CHAMBER IS BECAUSE THE 5.56 IS LOADED TO HIGHER PRESSURES. That means I'm saying it isn't a good idea to do so. Even though the rounds fit and fire intercheangeably.

    nononsense explained it to me once a long time ago. After I said it was okay to do it {again, it's not}. And, had in fact done it for years. I did notice my cases were pretty beat up after firing 5.56 in a .223 chamber.

    The leade, or amount of distance between the bullet and lands loaded normally from the case, in a 5.56 is longer than in the standard .223 chamber. This allows the bullet to not be held up immediately upon firing and produce that 'pressure spike' that can cause the damage. It is further alleviated when the bullets having the chance to get a 'run' at the lands don't hold up and cause as large of a pressure spike.
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  • Justjump
    Ok I'll respect the argument as it is one I had not considered. So tomorrow I'll do chamber casts of 3 commercial bolt guns and 2 DHBARs. Then I'll mix the ammo between the guns and chrono it. I understand freebore very well. I do understand that rounds over 60g could hypothetically make contact with the rifling. I just want to see some evidence of the argument. I'm pretty sure the commercial guns are1=10 or 1=12 I know the Hbars are 1=7
    O BTW the mil brass showed no excess pressure signs at all.
    I appreciate you sharing your understanding of it.


    Ok I did some research cause I'm curious. From what I can understand Mil spec ammo is NOT loaded to excessive pressure. The methods used From SAMMI and Nato are different. Internal case dimensions are different in that Mil ammo has somewhat thicker brass especially in the web area. I knew about thicker brass, thats why I always work loads up with much attention to this. Less capacity can cause higher pressure. Most of the pressure issues are originating from the bullet being to long and impressed on the rifling. If your commercial rifle (223) has a long enough throat then I suspect you wont see high pressure signs. We'll find out.
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  • givette
    This topic, over the years centered on autoloading military surplus, or paramilitary firearms. Folks usually concentrate on the chamber/boltface combo overpressure aspect, but the velocity of the reciprocation of the moving parts during the autoloading sequence is the area that may take a beating as well.

    What I've just said above is a broad-brush statement.

    In the rifles that use the Stoner design, the aforementioned 'pressure spike' has a direct effect on the locking lugs of the bolt, or the barrel extension locking lugs.

    Conclusion: Military 5.56 fired in a .223 chamber causes overpressure..and it's the distance of the freebore/leade that causes it. The bullet doesn't have to necessarily be touching the rifling lands. Best, Joe
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  • sandwarrior
    One thing about this cartridge. Even though it is a higher pressure, there is not the total case internal surface area that dictates maximum overall pressure. Meaning a case like the 5.56/.223 with an internal surface area of about 1.8 sq." is going to have a total pressure exerted outwardly of 106,880 lbs. If 60,000 psi is used. A 30-06, with 2.9 sq.", using 60,000 psi is going to have roughly 180,000 lbs. of total force exerted outwardly.

    4140 oil quenched & tempered steel has a yield strength of about 200,000 psi. So, the smaller case has steel around this that is about 4 times as strong as it is. The larger case about three times as strong. When dealing with that much flex with those kind of pressures, you can get away with more pressure in a smaller case.

    Not that any of that is a valid reason to shoot too high of pressures in your rifle. Because, in our modern firing systems, there is a huge joint where the bolt interfaces with the barrel/chamber. That is the weak point. Because it is filled with brass. Exceed that and you could burn your face off pretty quickly.

    Edit:

    quote:Originally posted by Justjump


    "...."

    Ok I did some research cause I'm curious. From what I can understand Mil spec ammo is NOT loaded to excessive pressure. The methods used From SAMMI and Nato are different. Internal case dimensions are different in that Mil ammo has somewhat thicker brass especially in the web area. I knew about thicker brass, thats why I always work loads up with much attention to this. Less capacity can cause higher pressure. Most of the pressure issues are originating from the bullet being to long and impressed on the rifling. If your commercial rifle (223) has a long enough throat then I suspect you wont see high pressure signs. We'll find out.


    Mil-spec ammo isn't loaded excessively for Mil-spec. It IS loaded to a higher pressure than SAAMI .223 Rem. 62,000 vs. 60, 000 (and more typically 58,000). There is also, "De-mil'ed" 5.56 ammo. That has been taken apart, the load reduced, and put back together.

    Also, yes, military brass is generally thicker than civilian brass. Or, as the military puts it in spec terms, "more robust". It's the same with 7.62, although pressure roles are reversed in that situation.

    And in keeping with good reloading practices, working up no matter what kind of brass you have is the smart thing to do.

    Anymore though, I always recommend getting the 5.56 chamber or at least a .223 Wylde, if you can. That way you can shoot both safely.

    Edit II:

    quote:Originally posted by Justjump
    Is there an absolute? What I mean is this, is there a demonstrable catastrophic failure that can be directly linked to anything other than lack of freebore (leade)???



    As far as rifles go, I can't tell you. I can tell you the brass from 5.56 I've used has had it's issues coming out of the chamber. Some loose/blown primers. Extractor marks on the head. I've had to toss some of it for split (burned through) necks on far fewer loads than I normally get. That is a good point though.
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  • Justjump
    Is there an absolute? What I mean is this, is there a demonstrable catastrophic failure that can be directly linked to anything other than lack of freebore (leade) (throat)???
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  • Sig220_Ruger77
    It is all about the "throat" in these two calibers. The average 5.56 rifle has a longer throat then the average .223 rifle. Firing a 5.56 round in the shorter throated .223 rifle can cause excess pressure. This over time can cause problems. I have done it myself and while I didn't incurr any major issues, I did experience signs of excess pressure on the case. I would therefore, not reccomend firing 5.56 ammo in a .223. The opposite(.223 in 5.56) is fine, like mentioned.

    Thats my opinion on the matter. [;)]

    Jon
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  • Justjump
    thats pretty much where I'm going with this

    I always want to know more than the wikipedia version, which is pretty much "cause I said so" [;)]
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  • Wolf.
    There is a very good, in depth discussion of the ammo in question in an article on a web site called The Gun Zone.
    http://www.thegunzone.com/556v223.html
    "5.56mm v. 223 Remington
    Disconfusing the issues of a couple of differences..."

    Rather than quote from that article, I'll leave it to you to read what they have to say.
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  • Justjump
    Thanks wolf!
    Good article
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