5.56 or 223?

kabar

January 11, 2013 14:33

NIB Colt M-4 carbine LE6920
Receiver is marked 5.56
Box is marked 223
What is it? Does it matter if you shoot 223 in a 5.56? I'm new to this type of gun so that is why I'm asking this.
Do you think the box might have been marked wrong? The serial numbers match.[?]

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  tsavo303

  January 11, 2013 14:51

  no colt can shoot either
  its fine

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  armilite

  January 11, 2013 15:59

  You can't shoot the box, you shoot the gun.

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  tsr1965

  January 11, 2013 16:07

  kabar,
  
  You can shoot the 223 Remington ammunition in a 5.56x45mm NATO chamber, but you shoule refrain from shooting the 5.56x45mm NATO, in a rifle chambered for the 223 Remington. Some 5.56mm ammo, can create high pressure problems in the 223 Remington chamber.
  
  Best
  
  EDIT 1
  
  quote:The difference between 5.56mm and .223 Remington cartridges isn't in the brass to any significant extent. Contrary to popular lore, military cases are not thicker or stronger but are more likely to be found annealed when purchased.
  
  That is PURE BS. Try cutting the Lake City brass in half lengthwise, and measuring the case thickness down by the web. If the outside dimensions ar the same, and inside volume are smaller, it has to be thicker somewhere. Why do all the bullet manufacturers say to start loads using military brass at 1 grain lower than starting, and work up? Are they full of BS too? I don't think they all can be.
  
  Best

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  BHAVIN

  January 11, 2013 21:27

  Go by what is stamped on the barrel. Again .223 in a 5.56 is okay not the other way around.

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  Mobuck

  January 12, 2013 03:00

  "Go by what is stamped on the barrel"
  This is the correct response. Disregard anything that might be "stamped on the receiver".
  If the barrel is marked 5.56, you can safely shoot any type or brand of .223 or milspec 5.56.

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  kabar

  January 12, 2013 05:04

  Thanks guys, I'd rather be safe than sorry. It is marked 5.56 on both receiver & barrel. It never hurts to ask.
  Have a Great Day![:)]

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  sandwarrior

  January 12, 2013 07:35

  quote:Originally posted by forgemonkey
  Here's a post from the GD forum this morning,,,,,,,the below was taken from the 'Ammoguide' website,,,,,,,,,,,,,,,
  
  
  .... <<{shortened to save space, not take out of context}
  
  In the field of .22 caliber centerfire cartridges, the round excels, generating chamber pressures in excess of 50,000 psi and muzzle velocities over 3000 fps. A new genre of highly-accurate 5.56/.223 rifles has evolved sporting heavy, floating target barrels with fast-twists (1-in-9" or faster), capable of stabilizing precision heavy low-drag bullets. This combination has proven itself a frequent winner at NRA Hi-Power rifle competitions, over high-energy cartridges such as the .300 Winchester Magnum at distances up to 1000 yards.
  
  NOTE: In rifles, common 55-gr. bullets may not stabilize with faster than a 1-in-9" or 1-in-8.5" rifling twist. Avoid lighter bullets if your twist is faster, heavier bullets if your twist is slower.
  
  

  ---

  
  
  
  
  A couple notes here even though they may be off topic. It's just good business to correct the truth:
  
  First, the .223/5.56 combination isn't beating the .300 magnum class anywhere, unless the magnum shooter isn't very good. What IS beating the .300's are the 6mm's and 6.5's with a few 7mm's smattered in there. Same style bullet as the .223/5.56 but slightly larger diameter and much longer. Naturally, all the above have a lot less recoil than the .300 magnum class.
  
  Second, the 1-9" twist will stabilize a 55 gr. bullet. It seems to be a common misunderstanding gunwriters have about simple physics. A tighter twist will stabilize the bullets but can affect accuracy based on how concentric the lighter bullets are. The faster spin exacerbates the 'wobble' a bullet has due to non concentric core/jacket issues. FWIW, no bullet is perfectly round or concentric, just as close as we can make them. Which today is very close. 55 gr. bullets of yesteryear had a lot to be desired. Therefore, they show the worst accuracy while being over-rotated.

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  5mmgunguy

  January 13, 2013 06:13

  The primary thing that requires a faster twist is bullet length, but there are other factors, none are as influencing as length. The 1-9 twist will not only stabilize a 55 gr bullet but actually will spin the bullet faster than it needs to be for optimum stabilization.

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  nononsense

  January 13, 2013 07:24

  kabar,
  
  Nothing like a good picture to explain the difference:
  
  .223 Remington Chamber Cross Section
  
  
  
  5.56mm NATO Chamber Cross Section
  
  
  
  Drawing to explain the terminology
  
  
  
  Best.

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