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Shooting .223 in a 5.56 rifle

Discussion in 'Rifle Country' started by Angleiron, Dec 2, 2009.

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  1. Angleiron

    Angleiron Member

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    I bought my 5.56 because of the versatility of being able to shoot both types of rounds in a pinch, and was wondering if anyone else is shooting .223 in their 5.56 rifle? I know that it is not as accurate as a shooting these rounds out of a designated .223 rifle, but how much of a difference is there? I have the opportunnity to get 1000 rounds of .223 for a real good price, but if it is a big difference then maybe it is not worth it.
     
  2. TexasRifleman

    TexasRifleman Moderator Emeritus

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    Accuracy wise I've never been able to tell any difference.

    I mean, if it's surplus junk 5.56 I'm shooting maybe, but in general I never notice enough difference to worry about for every day shooting.
     
  3. stacks04

    stacks04 Member

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    accuracy should not suffer either.
     
  4. mongoose33

    mongoose33 Member

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    I bought mine in 5.56 for the same reason; I don't notice any difficulties.
     
  5. rcmodel

    rcmodel Member in memoriam

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    There is more variety of accurate .223 loaded by the factories then there is 5.56.

    Most of the 5.56 is loaded with FMJ-BT GI style bullets.
    And none of them will prove to be as accurate as any of the .223 match or varmint bullet loads.

    As for best accuracy?
    Your chance of best accuracy in a 5.56 chambered gun is .223 match or varmint ammo.
    Followed by, or equaled by 5.56 Match ammo.

    5.56 FMJ-BT will be at the very bottom of the accuracy heap in either chamber in any gun.

    rc
     
  6. wishin

    wishin Member

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    As I understand it, the .223 has a tighter chamber around the neck and is shorter which purportedly allows for a little more accuracy. RRA's Wylde chamber is supposed to "correct" this so .223 and 5.56 are equally as accurate.
     
  7. Boba Fett

    Boba Fett Member

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    Same.

    No issues and accurate enough as far as I can tell. If I want more accurate I'll get a bolt gun and use match ammo.
     
  8. W.E.G.

    W.E.G. Member

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    .223 ammo is OK in 5.56 barrel.

    5.56 ammo is not OK in .223 barrel.

    This was reported in the American Rifleman magazine recently.

    .223 chamber is "smaller" than 5.56 chamber.

    [​IMG]

    .223 Remington vs. 5.56: What’s In a Name


    By BRYCE M. TOWSLEY field editor
    American Rifleman – September 2007


    Most gun guys know the history of the .223 Remington and that it - like so many of our popular cartridges - started life in the military. Because the military switched to metric designations sometime in the 1950s, this little .22-cal. cartridge was later called the 5.56x45 mm NATO (commonly referred to as "5.56x45 mm").

    The 5.56x45 mm surfaced in 1957 as an experimental cartridge in the AR-15 rifle. The concept was to develop a smaller, lighter military cartridge that would still be traveling faster than the speed of sound at 500 yds., and this was accomplished by using a 55-gr. boattail bullet. The AR-15 evolved into the select-fire M16 rifle that was adopted by the military in 1964.

    Even though it would ultimately kill off its own .222 Rem. and .222 Rem. Mag. cartridges, Remington was quick to act, and very shortly after the military adopted the 5.56x45 mm cartridge the firm brought out the civilian version, called the .223 Remington. Confusion followed.

    The common misconception is that the two are the same; that 5.56x45 and .223 Rem. are the same dance partner, but with a different dress. This can lead to a dangerous situation. The outside case dimensions are the same, but there are enough other differences that the two are not completely interchangeable.


    One big difference is pressure. It becomes a bit confusing, as the pressure for the two is not measured in the same way. The .223 Rem. is measured with either Copper Units of Pressure (c.u.p.) or -- more recently -- with a mid-case transducer in pounds-per-square-inch (p.s.i.). The military 5.56x45 mm cartridge is measured with a case mouth transducer. The different measuring methods prevent a direct comparison, as a case mouth transducer gives lower numbers on identical ammunition when compared to those from a midcase transducer. That's because the pressure is measured later in the event, after the pressure has already peaked. According to Jeff Hoffman, the owner of Black Hills Ammunition, military ammunition can be expected to hit 60,000 p.s.i., if measured on a Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) mid-case system. Black Hills loads maximum average pressure is 55,000 p.s.i., while a 5.56x45 mm measured with a case mouth transducer has a maximum average pressure of 58,700 p.s.i.

    While the 5.56x45 mm chamber is slightly larger than the .223 Rem. chamber in just about every dimension, the primary difference is throat length, which can have a dramatic effect on pressure. The 5.56x45 mm has a longer throat in the chamber than the .223 Rem. The throat is also commonly called the leade, which is defined as a portion of the barrel directly in front of the chamber where the rifling has been conically removed to allow room for the seated bullet. Leade in a .223 Rem. chamber is usually 0.085", while in a 5.56x45 mm chamber the leade is typically 0.162", or almost twice as much as in the .223 Rem. chamber. Also, the throat angle is different between the two chambers, and that can affect pressure rise and peak pressure.

    SAAMI regulates cartridge overall length, but not bullet ogive design. The shape of the ogive can significantly affect how far the bullet jumps before contacting the rifling. Some 5.56 mm bullets have an ogive suitable for 5.56 chambers with the longer throat, but if they were chambered in a .223 Rem., it could result in very little, if any, "jump" to the rifling. This can increase pressures. Remember, the 5.56x45 mm already starts out at a higher pressure. If the higher-pressure 5.56x45 mm cartridge is then loaded into a .223 Rem. firearm with a short throat, the combination of the two factors can raise chamber pressures.

    If you are a handloader, you must also consider that the 5.56x45 mm cartridge case may have a thicker sidewall and a thicker head, which were designed to withstand the stresses generated by the higher chamber pressures. This reduces the powder capacity of the case. If the 5.56x45 nun case is reloaded with powder charges that have proven safe in .223 Rem. cases, this reduced internal capacity can result in much higher chamber pressures.

    Bottom line? It is safe to fire .223 Rem. cartridges in any safe gun chambered for 5.56x45mm. But, it is not recommended and it is not safe to fire 5.56x45 nun cartridges in a firearm chambered for .223 Rem.

    In fact, the 5.56x45 mm military cartridge fired in a .223 Rem. chamber is considered by SAAMI to be an unsafe ammunition combination and is listed in the "Unsafe
    Arms and Ammunition Combinations" section of the SAAMI Technical Correspondent's Handbook. It states: "In firearms chambered for .223 Rem. - do not use 5.56x45 mm Military cartridges."

    There is no guarantee, however, that .223 Rem. ammunition will work in 5.56x45 mm rifles. Semiautomatic rifles chambered for 5.56x45 mm may not function with .223 Rem. ammunition because they are designed to cycle reliably with the higher pressure and heavier bullets of the 5.56x45 mm particularly with short barrels. While problems are rare, they do not indicate that the ammunition or rifle are defective. Like some marriages, they are simply incompatible.

    When shooting .223 Rem. cartridges in a firearm chambered for 5.56x45 mm, it's likely that there will be a degradation in accuracy and muzzle velocity due to the more generous chamber dimensions. That's not to say that a firearm chambered in 5.56x45 mm won't be accurate with .223 Rem. loads, only that, on average, the .223 Rem. chambered firearms will be more accurate with .223 Rem. ammunition than rifles chambered for 5.56x45 mm firing .223 Rem.

    Another issue is the twist rate of the rifling. The SAAMI specification for .223 Rem. is a 1:12" twist, and most non-AR-15-type rifles will use that rate. But, this is a cartridge that crosses a wide spectrum of uses, and as a result there is often a wide deviation from the 1:12" twist rate, particularly in the very popular AR-15-style "black guns." There are bullets available for the .223 Rem. that range in weight at least from 35 grs. to 90 grs. With that wide of a spectrum, one twist rate is not going to be enough.

    Firearms chambered for 5.56x45 mm often have a rifling twist rate of 1:7" to stabilize the long, sleek, heavy bullets used in long-range shooting. Any rifle with a 1:7" twist rate will work best with bullets heavier than 60 grs.

    On the other hand, a 1:12" twist rate (most bolt-action .223 rifles) will stabilize most bullets up to 60 grs., however some longer 60-gr. bullets will not shoot well with that twist rate. Many firearms use a 1:9" twist, which is a very good compromise that works well with most bullets up to 70 or 75 grs. The great thing is that if you have a good barrel and quality bullets, the 1:9 works well with even the lightest bullets.
    What does all this mean? If you have anAR-15 type firearm with a 5.56x45 mm chamber you can shoot either .223 Rem. or 5.56x45 mm safely. If your twist rate is 1:7" you should use bullets weighing 60 grs. or heavier. If you have any rifle with a 1:12" twist you should shoot bullets of 60 grs. or less for best accuracy. If you have a .223 Rem. rifle of any type, it is not recommended that you use 5.56x45 mm ammunition.
     
    Last edited: Dec 2, 2009
  9. McBuck

    McBuck Member

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    So...what is the chambering for a new 580 Mini-14, when the owners manual and the stamping on the gun says ".223 or 5.56" ? Ruger says the gun will accept 5.56. I have no reason to doubt that. I will probably only ever use .223 but what if I ever need/have the opportunity to use 5.56 ?


    Great thread by the way ! Informative.
     
  10. TexasRifleman

    TexasRifleman Moderator Emeritus

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    Mini-14's have always been 5.56 chambers, I don't believe that has changed with the new models. Their engraving a novel on the side of the rifle seems to get worse every year though :)
     
  11. sandkicker

    sandkicker Member

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    I hate to have my first post on this forum to be a disagreement, however:

    Re: "Mini-14's have always been 5.56 chambers"

    Should read "Mini-14's made since 1986 have 5.56 chambers"
     
  12. SaxonPig

    SaxonPig Member

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    Once again, #32 covers this VERY popular topic.


    223 vs. 5.56 (and .308 vs. 7.62x51).

    32. There is essentially no difference between commercial .223 and military 5.56 ammo. The same is true with .308 and 7.62 ammo. The military stuff has slightly thicker brass with a tiny bit more length in the shoulder and I hear this is for strength when feeding through full-auto guns that tend to slam the rounds into the chamber violently. But otherwise, there doesn’t appear to be any difference that I have noted after many years of shooting both military and commercial ammo through my .223 and .308 rifles, both bolt action and semi-auto although with some guns with tight chambers closing the bolt on military ammo can be a bit snug. The military 5.56 ammo is loaded to very slightly higher pressures than commercial .223.
     
    Last edited: Dec 2, 2009
  13. Maverick223

    Maverick223 Member

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    I am pretty sure that is not true either, as I believe the "target" model is chambered for .223, and 5.56 is not recommended.

    :)
     
  14. Boba Fett

    Boba Fett Member

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    And yet SAAMI's site says it is unsafe and not to use 5.56 in a 223.

    http://www.saami.org/Unsafe_Combinations.cfm


    Fulton Armory doesn't think it's really a good idea either:
    http://www.fulton-armory.com/556-vs-223-Chambers.htm
    From Winchester:
    http://web.archive.org/web/20080505.../lawenforcement/news/newsview.aspx?storyid=11

    So, yes...you can shoot 223 from 5.56, but shooting 5.56 from 223 is unwise and possibly dangerous.

    Now, some people may shoot 5.56 from 223 and not have issues...yet.

    I just wouldn't want to be the one person that proves why manufacturers and organizations warn against it.
     
    Last edited: Dec 2, 2009
  15. SaxonPig

    SaxonPig Member

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    Case dimensions are identical. I have shot hundreds of military 5.56 through several commercial bolt and semi-auto rifles without incident. That's all I know.

    http://stevespages.com/jpg/cd223remington.jpg

    http://stevespages.com/jpg/cd556nato.jpg

    I did make a slight correction. The military ammo is loaded a tad hotter. I doubt it's enough to make a difference. Yes, the SAAMI lawyers tell them to say using 5.56 in a .223 is unsafe. All reloads are unsafe, too, you know.
     
  16. wishin

    wishin Member

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    My target model is marked .223 caliber on the receiver.
     
  17. Maverick223

    Maverick223 Member

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    How does it shoot? I get the feeling that despite the target name it still isn't a bench gun. Not trying to bash them (don't know about the target variant, but the new ones are much improved over the former series), as I rather like the Mini, just wondering.

    :)
     
  18. wishin

    wishin Member

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    I've been very pleased with the groups using 68 gr. Ultramax. Getting consistent 3/4' 3 shot groups from a bench rest with bipod, with an occasional flyer. I tried many different factory brands and various bullet weights. It loves the Ultramax loads.
     
  19. Maverick223

    Maverick223 Member

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    Not bad at all, glad to hear that it shoots well. You need to post a group in Krochus' Mini Match...you might just win. ;)

    EDIT: In case you're interested, Here is a link to the match.
     
  20. possum

    possum Member

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    welcome to thr.

    for the type of training i do and in the context of which i train with my ar, the accuracy difference if there is one is not somthing that i am worried about, and honestly something that i have never had an issue with.
     
  21. Offfhand

    Offfhand Member

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    Just curious, has anyone ever heard of 5.56 ammo causing problems in a .223 Rem bolt rifle?
     
  22. rcmodel

    rcmodel Member in memoriam

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    Yes, I have.

    Many years ago, SAKO made some Vixen's with .223" bores instead of .224".
    They were also tight chambered in .223 Rem.

    Along the same time, Remington was making .223 Rem Model 40-X target rifles with very tight .223 Rem match chamber dimensions.

    There were reports of blown primers in both guns when shooting higher pressure 5.56 ammo in them.
    No harm was done to the shooters.

    That is the only two instances I have ever heard of.

    I hate for you to be wrong too, but you are.

    All Mini-14's, since day one, have been chambered for .223 and 5.56.
    It says so in the owners manual.

    Mini-14 Series 180 1974 - 1977.
    http://www.ruger-firearms.com/products/_manuals/mini14-180.pdf

    The only exception is the current Target model which is chambered for .223 only.

    rc
     
  23. greyling22

    greyling22 Member

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    so if I took 5.56 brass and reloaded it in a .223 die set with .223 load data (not a hot load, just a middle range one) would it be safe to shoot in a .223 chamber?
     
  24. Maverick223

    Maverick223 Member

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    I don't see why not, and it should last a little longer than .223 brass. Furthermore, I have never heard of or seen "5.56 dies", as the case is identical (with exception of thickness). I can tell you that .223 dies work just fine for my 5.56 (brass and rifle).

    :)
     
  25. Boba Fett

    Boba Fett Member

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    Other than that I don't see any reason it wouldn't work.
     
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