Is It Safe To Shoot 5.56 in a .223 AR-15?

BY Herschel Smith
1 month, 2 weeks ago

As I think about it, the only thing I ever thought it might do to consistently shoot 5.56mm in a rifle chambered for .223 is throat erosion.  I think they confirm that.


Comments

  1. On September 1, 2021 at 1:49 am, Georgiaboy61 said:

    The difference between 5.56×45 NATO and .223 Remington – both of which fire .224-caliber bullets -lies not just between the cartridges themselves, but the firearms and purposes for which they are designed.

    5.56x45mm NATO is the current standard (“stanag”) assault rifle and light machine-gun round for the NATO alliance, whereas .223 Remington is its civilian sporting counterpart.

    Excepting precision, match-grade sniper and competition weapons/platforms and the like, most military weapons chambered in 5.56×45 are select-fire capable, meaning that they may be used not only for single shot semi-automatic fire, but cyclic fully-automatic fire. Such fire may be of extended duration, under harsh environmental conditions, and when the weapon is already dirty, fouled or otherwise in a state of less-than-optimal condition.

    In order to handle the additional mechanical, chemical and thermal stresses associated with heavy-duty military use, the cartridges such weapons fire must themselves be robust and possess the needed durability and consistency to function even under hard use in the field.

    To this end, the 5.56×45 NATO case is somewhat stiffer and more-rigid than its civilian analogs such as the .223 Remington, and may contain additional thickness of material at high-stress areas such as the case head and rim. The bullet is crimped into the case mouth in order to lessen the chance of bullet set-back under recoil while in the magazine or when it is being chambered.

    The added strengthening in the case head and rim area is to lessen the possibility of a torn case or case-head separation during extraction and ejection, when the case may still be hot and therefore somewhat softer than when cool.

    Uniform ammunition manufacturing to a given alliance-wide standard assures that any 5.56×45 round will function in any of the NATO small arms chambered for it. A small “x” or cross inside a circle is the identifying mark signifying this, next to the manufacturer’s head-stamp on the cartridge base adjacent to and surrounding the primer pocket.

    A degree of accuracy is sacrificed in NATO military weapons, to enhance the reliability of these small arms. The longer throat is one of these trade-offs. It enhances positive chambering, but at the expense of consistency of bullet seating and therefore accuracy. Compared to a precision rifle, chamber dimensions are generous, both to aid in function and also in cooling.

    A civilian market firearm in .223 Remington, however, such as a bolt-action varmint rifle, can be made to much tighter tolerances, since its operating conditions are typically much more favorable and forgiving than those endured by mil-spec arms. Seldom, if ever, will it be used for long strings of fire, and it has the opportunity to cool between shots much better than a cyclic LMG or assault rifle. Even a semi-auto design using .223 has it easier than its military counterpart.

    Since civilian sporting use is typically much less-demanding in terms of wear-and-tear than military use in the field and in combat, the ammunition also can be designed differently. Since it is not typically destined for use in full-auto weapons, .223 Remington cases can be made thinner and less-rigid than their mil-spec 5.56×45 counterparts. This is also the case since the civilian sporting chamber is tighter and has a shorter throat, which aids accuracy but at the expense of some reliability when it is fouled and/or hot.

    Some civilian .223 ammo is made by companies which also supply the military market, such as Federal and Black Hills. Their military-issue and civilian ammunition in 5.56×45 and .223 don’t differ all that much, or do not always do so. The weighing of the cases from each confirms that both have about the same mass. Other firms cut corners with their civilian-market ammo, and it isn’t up to the durability standards of true stanag NATO ammo.

    As for peak pressures, the video pretty much gets that right. Proof pressures for firearms that are chambered for .224-caliber ammunition, whether civilian or military use, are generally well-above the peak firing pressures seen in either commercially-available 5.56x45mm NATO or .223 Remington. There are variations, but in general, 5.56 runs about 5-10% hotter than .223 Remington, in terms of MV from the same barrel.

    One final point, in closing: Many ammunition re-manufacturers, who make reloaded ammunition under license for commercial sale, do not distinguish between 5.56 and.223 cases when collecting brass for their production runs. Those guys don’t want any trouble with lawyers or regulators; if there was a difference worth mentioning between the two in terms of risk, they wouldn’t intermix the recycled cases that way.

  2. On September 1, 2021 at 6:37 am, Russell G. said:

    @Georgiaboy61; Last para. Probably true. The differences in cases (and I’m mainly going by FC brass and LC plant) is that NATO 5.56 cases have greater thickness under the primer flash hole (aka the “web”), relative to the LC 223 consumer stuff. By about 0.030 on a good day, with LC NATO being on the fat side. The weight of the LC NATO brass is also different than 223 consumer stuff (some people weight out the brass when they load up the set and try to make bugholes on paper). The practical consequence of this is that for reloaders you get more re-dos on NATO brass before the primers start getting so loose that you can push them back out. That’s about 5 times for FC LC NATO, but benchrest shooters generally don’t go to max SAAMI on anything (usually 75-85% on Quickload). On the NATO brass the primer pocket rim is also stamped to secure the primer for some ridiculous reason, and you generally champher that off before you put your first primer back in. So, bottom line is that the actually difference relates more to the bullet “jump” (not COAL) in the different chambers, and you’re right about the pressure issues (and the galactically shitty accuracy of NATO stuff). So, 1X fired brass on remanufactured ammo is merely breaking the neck annealing in…It’s fine.

  3. On September 1, 2021 at 2:19 pm, Stuart said:

    If 5.56 was unsafe in .223 rifles due to pressure, it would mean that the makers of .223 rifles are intentionally using weaker steel than 5.56 rifle makers. Does that sound like reality to anyone?

    IIRC, this whole nonsense was started as lawyer proofing by Sturm, Ruger & Co. to counter claims that the above paragraph was true. (at the time Ruger only chambered 223) Remember, these are the same assholes that for many years refused to sell us RifRaf the high capacity magazines they sold our overlords.

    Oh, and .223 pressure standards are exactly the same as 5.56 in Europe (CIP standards)

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You are currently reading "Is It Safe To Shoot 5.56 in a .223 AR-15?", entry #28021 on The Captain's Journal.

This article is filed under the category(s) Ammunition,AR-15s and was published August 31st, 2021 by Herschel Smith.

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