223 vs 5.56 accuracy

Discussion in 'General Rifle Discussion' started by montveil, May 29, 2014.

  1. montveil

    montveil New Member

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    I realize the 223 case is slightly smaller than the 5.56 case.
    With the 5.56 chamber being larger, how does that affect accuracy when the 223 is fired in a 5.56 chamber.
    It would seem that the looser 223 round would result in poorer accuracy.
    Also, if a 223 round is fired in the 5.56, does that case now not fit a 223?
     
  2. JonM

    JonM Moderator

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    Chamber is just very very very very very slightly longer in 556 than 223 but its so close that for all intents the same gages can be used on either. Even then it depends on who is setting the headspace in the first place. Leade is a little longer in 556 allowing use of longer ogived bullets.

    You can get great accuracy with either chambering since the factors that determine accuracy aren't in the chamber itself. It has more to do with the type of rifling the condition of the throat how far the bullet is from the rifling the powder used the consistancy of the ammo the type of metal the barrel is made from and any coatings how smooth the rifling is cut.

    Want a great sccurate barrel look more at who is making the barrel and how and what its made from along with the specs.

    As for once fired cases. It doesn't matter. When its resized the dies are the exact same for 556 and 223. Its where you set the shoulder that matters. All semi auto brass should be full length sized. Fire forming brass on a semi easily causes feed issues. The brass is still under some pressure and hasn't fullly shrunk before it starts being extracted. This means the case can be slightly larger than if it sat there until manually extracted.

    Typically 556 chambers aren't used on accuracy builds so your not going to find that on a barrel built for accuracy unless you special order such from a barrel maker.
     

  3. 303tom

    303tom Well-Known Member

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    There is NO difference in the two rounds, just in the chamber of the firearm !..........
     
  4. Axxe55

    Axxe55 The Apocalypse Is Coming.....

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    the only rifle i have currently in 5.56/223 is my Bushmaster AR Carbine. i generally use the PMC 55 gr. FMJ rounds or the PMC X-Tac 62 gr. Green Tips. i really am not seeing a big difference in accuracy between the two rounds in my rifle.

    the barrel on mine is marked 5.56 Nato, 1-9. the lower reciever is marked 223-5.56mm Nato.
     
  5. Highpower

    Highpower New Member

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    JonM nailed it.

    Gun at left has a factory Colt 5.56 chrome lined barrel w/ 1:7 twist.
    Gun at center has a Krieger .223Rem stainless steel barrel w/ 1:7.7 twist.

    I shoot Lake City 5.56 military brass is both guns. However.... I do keep the brass segregated between the two guns, because I resize them to fit the individual chambers of the rifles.

    Accuracy between the two is like night and day, just because of the quality and construction of the Krieger barrel - not because of it's caliber designation. Of course hand loading ammunition to properly fit any particular chamber goes a long way too, in getting the most accuracy possible from any gun ..... in my experience.

    [​IMG]
     
  6. montveil

    montveil New Member

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    so if you shoot the 5.56 ammo in the 223 why is it such a no-no by some sources. Does the 5.56 have higher pressures?
    Why can't one just ream out a 223 barrel to fit the 5.56?
     
  7. Axxe55

    Axxe55 The Apocalypse Is Coming.....

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    apparently from some sources the 5.56 operates at a higher pressure than 223 ammo does. some sources say the cases are externally the same but that the interior dimensions are smaller on the 5.56 vs. the dimensions internally of the 223 cases.

    please don't quote me on that. this debate has been ongoing for years now and i don't have a clearcut answer yet on this. but my thoughts are this, i use what is marked on the rifle as to what i would fire in a particular rifle.
     
  8. jjfuller1

    jjfuller1 New Member

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    there is no need for that.. the bullets would still be the same diamieter(.224)
     
  9. JonM

    JonM Moderator

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    Because of the leade in the throat. 556 has a bit longer space between the case mouth and the start of the rifling. This is to accomodate things like tracers ap and other special 556 ammo. The design of bullets for the 556 allows for a longer ogive. If you stick a pulled bullet from a military cartridge in a handloaded case and use 223 spec cases you still run a risk of kaboom.

    You can use 556 in a 223 if you use a bullet comparater like the hornady one to find the max coal of a 223 rifle then measure the 556 cartridges at the ogive to be sure the round doesnt hit the rifling on chambering. To do this you need to send a once fired case out of that rifle to hornady to make a modified case for measuring. Cost is about 5$ not counting shipping. May be a bit more nowadays.

    You can ream out to 556 spec but you have increase leade in the throat and thats not an easy thing to do without proper tools. For example the wylde chamber uses a 223 chamber with a 556 throat. The issue isnt really the chamber itself.
     
    Last edited: May 29, 2014
  10. JonM

    JonM Moderator

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    This if your buying off the shelf.

    If your a handloader just order the right case gages to start with and go from there. Have a bullet comparator and appropriate modified cases made from new once fired brass in that specific gun. Set your dies using the correct case gage test your coals on cartridge and rifle from the ogive stay within published book load data and you wont have issues
     
  11. Highpower

    Highpower New Member

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    Please note that I wrote that I use 5.56 military brass, not loaded ammunition. I should have made that more clear - my bad.

    5.56 NATO ammunition produces higher pressures than .223Rem ammunition that is loaded to SAAMI specifications. One of the reasons for the higher pressures in military ammo is indeed because of slightly thicker case walls near the case head, which reduces the internal volume of the case slightly.
    Slice one of each down the center and you'll see the difference.

    Reloading your own ammunition has many more elements to be concerned with versus shooting ammo out of a box. Just be sure that whatever ammo you use is safe to use in that gun.
     
  12. Egreen96

    Egreen96 New Member

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    If you want to use both 5.56 and .223 I would look for a .223 Wylde chamber it's meant to handle both rounds


    Sent from my iPhone using Firearms Talk
     
  13. 303tom

    303tom Well-Known Member

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    You have Sizer Set`s for individual chambers ?................
     
  14. 303tom

    303tom Well-Known Member

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    Most all your chambers are Wylde chamber`s now a days..............
     
  15. bradam

    bradam Member

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    According to the 9th edition of Hornaday handbook: " The main differences between the 5.56 NATO and the 233 Remington is the operating pressure and chamber throat. SAAMI maximum pressure for the 223 Remington is 55,000psi. The 5.56 NATO is loaded to 60,000 psi. Chamber throat for the 223 Remington is shorter than 5.56 NATO chambers as well. It is not recommended to shoot 5.56 NATO ammunition in a 223 Remington chamber. Firing nato (higher pressure) in a a 223 Remington (shorter throat) rifle can cause pressure related damage that could lead to injury." The above was quoted directly from the 9th edition Hornaday handbook of cartridge reloading. Now IMO, match the cal. on the rifle barrel to the data in the reloading book. At least for now, I trust the judgement of the data in the reloading books.:)
     
  16. JTJ

    JTJ Well-Known Member Supporter

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    I have a bolt action Mossberg MVP factory chambered for 5.56x45. I can shoot both rounds with excellent accuracy. 223 spec hand loads are running sub MOA. I had a small amount of surplus that was shooting right at 1 MOA but that is not the norm for surplus ammo. The last batch I tried was running at 2 MOA. It will shoot good 223 commercial loads at the 1 MOA mark. I have not tried any steel case in it. Dont expect great accuracy if you shoot cheap ammo in any rifle.
    Most rifles would handle the 5k psi pressure overload with out a problem but the short leade and a longer bullet can cause a much greater pressure peak which can overload the action. Get a gunsmith to run a Wylde chamber reamer in the rifle if you want to shoot both.
     
  17. John_Deer

    John_Deer New Member

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    I don't shoot much paper with my rifle. It is a fun gun just like most 22 LR. I am not going to mount a bipod on the rifle or haul a bunch of sandbags around. We shoot it off hand with inexpensive federal soft point 223 ammo. The DPMS is chambered for 5.56. Almost everyone that shoots the rifle hits the target. We just use a peep sight similar to the sight that came on the rifle. If one can hit a golf ball at 100 yards or more the rifle and ammo are doing their job.

    You are going to get different results from different rifles. I am not scared to wear out the barrel by cleaning the rifle, so it doesn't have powder rings in the throat. I don't shoot the 223 at coyotes or fox to really see what it can do. I have rifles that buck the wind much better. I have had these rifles much longer and know what to expect from them.
     
  18. Axxe55

    Axxe55 The Apocalypse Is Coming.....

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    my 6th Edition of the Nosler reloading manual says pretty close to the same thing. if i were reloading 223, this is the information i would defer to. right now 223 is one of the few calibers i don't reload for right now. that maight change shortly.

    another issue that does make a bit of difference is the barrel twist of the rifle and the bullet weights it can work with accurately. most but not all bolt action rifles in 223 are designed with faster twist ratios for smaller bullets for varmint hunting, while most AR platformed rifles in 223/5.56 are slower twist ratios designed for mid to heavier bullet weights. so matching bullet weights to the twist ratio of the rifle is going to aid in increased accuracy.
     
  19. jjfuller1

    jjfuller1 New Member

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    i believe you have them reversed.. faster twist for heavier bullets( they need to spin faster to stabalize). slower for lighter bullets( can spin slower to stablize).
     
  20. Axxe55

    Axxe55 The Apocalypse Is Coming.....

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    you're right, i did have them reversed! the higher the number the slower and the lower the number the faster.

    brain fart moment!:eek: