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223 Remington (5.56MM NATO)


In 1964, Remington commercially standardized the 223, after the U.S. Military adopted the same round, known as the 5.56 NATO.  Design of the 223 case derived from the shorter 222 Remington.  To achieve the ballistics specified by the Military, in the initial design, the experimenters lengthened the case body 0.2-inch, with no other changes.  Then, for some reason, the Military specified a slightly shorter cartridge length and a significantly shorter case length.

The body was shortened 0.030-inch, the neck was shortened 0.117-inch, and cartridge overall length was shortened 0.02-inch.  The new case length and cartridge length allowed use of an ogive that was about 0.1-inch longer without that protruding below the case mouth, this made it feasible to improve the BC of the bullet, which matters a lot when considering shots past point-blank range.  Pressure specification was increased enough to offset the reduced case capacity.

As a varminting round, the 223 Rem is an excellent choice with wide availability both in rifles chambered for it and in handloading components.  With modern 40-grain tipped bullets it comes close to matching the trajectory of the original 22-250, 55-grain SP load.  Such loads are entirely effective for shots to about 400 yards.

Remington later standardized the orphaned, would be military round as the 222 Remington Magnum.  But with the lower pressure, it was ballistically indistinguishable from the 223, so it soon enough failed.  This is too bad.

The longer neck makes the 222 Rem Mag a fine round with better barrel life than the 223 Rem.  It was particularly desirable for the handloader who could use longer overall length.  This increased usable capacity and made it possible to use longer bullets without having to seat those with the bullet base well below the case neck.  Norm Johnson was a big fan of this round and many of his published articles (Precision Shooting magazine and others) extolled its value for varmint hunting.

Despite inauspicious early results (see below), the M-16, 5.56 NATO combination grew into an extremely serviceable and effective pair.  Improved propellant, modification to gun design, adoption of a quicker rifling-twist rate, and use of a heavier bullet each contributed to making the combination into a worldwide-recognized top-choice as a battle-rifle.

The heritage of this case dates to the 38 Colt cartridge of the 1860s and before that with the 1839 introduction of the 36 Colt Paterson cap-and-ball Revolver.

The text associated with the cartridge description reflects opinions and conclusions of the author, M.L. (Mic) McPherson. Lee Precision and its employees do not necessarily either agree or disagree with any of his comments. We present these with due deference to his recognized expertise in the firearms field. His acumen extends to handloading and all aspects of ballistics - internal, external, and terminal.
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