A few days ago, a Sergeant of the Military Police of the State of Los Angeles, who is also the shooting instructor of that institution, sent a commentary in one of our articles asking us to explain to him what the differences between the 5.56x45mm NATO and the. 223 Remington. But before we respond, I would like to congratulate this Sergeant for seeking more information to use in his instructions. Unfortunately we do not see so many professionals seeking a deeper knowledge of the equipment they use daily, whether these professionals from the Public Security forces or not.
But to talk about the differences of these two calibers we should go back a bit in 1957 when the 5.56x45mm NATO caliber appeared to be used for testing on AR platform with noveske lower rifles. The concept of this caliber was that a smaller, lighter military ammunition would be developed, and that at 467 meters (500 yards), it could still be at supersonic speed, and that’s what they did with a projectile boattail of 55gr.
Even though Remington knew that this caliber would kill the .222 Remington and the .222 Remington Magnum, Remington quickly, after the military adopted the 5.56x45mm NATO, released the civilian version of this caliber, it was called .223 Remington. And that’s when all the confusion started.
It is a misconception to say that the 5.56x45mm NATO and .223 Remington gauges are the same. That said, it could lead to some dangerous situations for operators of these weapons. Although they seem identical on the outside, there are some differences that make these calibers not interchangeable between their weapons.
One of the big differences between them is the pressure and the attachment used like noveske kx3 and the aero lower. It’s a bit confusing to talk about this, because the way to measure NATO’s 5.56x45mm pressure is different from that of Remington’s .223. The .223 Remington is measured in either Copper Units of Pressure (CUP ) or, more recently, PSI ( Pounds-per-Square-Inch), using a piezoelectric transducer in the half of the capsule. The military version, the 5.56x45mm NATO, is also measured in PSI, but the transducer is placed in the mouth of the capsule. The different forms of measurement already avoid a direct comparison, since the numbers reported in the NATO 5.56x45mm measurement are smaller, even if the same ammunition is used when measuring the .223 Remington PSI. This happens because the pressure is measured later, after it has reached its maximum peak.
According to Jeff Hoffman, owner of the Black Hills Ammunition, military ammunition and noveske kx3 expert can reach 60,000 PSI, as measured by SAAMI ( Sporting Arms and Ammunition Manufacturers’ Institute) in the same way as the .223 Remington is measured. While the .223 Remington can reach a maximum of 55,000 PSI, and when the 5.56x45mm is measured with the transducer in the mouth of the capsule, it reaches the maximum of 58,000 PSI.
Another major difference is that normally the lead (space between the beginning of the raid in the barrel and the end of the chamber) of armaments in 5.56x45mm NATO is of 0.162 “and the lead of weapons in .223 Remington is of 0,085. That is, the leade weapons in NATO 5,56x45mm is almost twice that of the .223 Remington also the angle that leade is also different between these weapons and all this generates an increase in both the overall pressure in armament and pressure peaks.
Because the projectile makes almost complete contact with the barrel rationing in .223 Remington armaments, which possess short lea , a dangerous situation is created when firing ammunition at 5.56x45mm NATO. Camera pressures can increase dramatically and catastrophic failures can occur.
The opposite, firing ammunition .223 Remington in a 5.56x45mm armament NATO, which has the long leade , is not so dangerous, what may happen is the loss of speed and accuracy in the shots, but serious failures on account of large increases in pressure, can not happen.
NATO 5.56x45mm capsules have thicker walls, this is designed to withstand the stress generated by the high pressures inside the chamber with its noveske kx5 attachment. This reduces the amount of propellant that can be put into it. If a 5.56x45mm NATO capsule is used to be loaded with the same amount of gunpowder that is safe in an ammunition.222 Remington, because the walls are thicker and smaller, when firing this ammunition, high pressures can also be generated.
However, several rationing steps are used in the arms of these calibers, each for a certain type of projectile. A 1:12 “raid pitch (most are .223 Remington bolt action rifles) will better stabilize projectiles up to 65gr. Already a step of 1:14 “, will be better employed if you use ammunitions of up to 55gr. Pipes of 1: 8, are better suited to projectile munitions up to 80gr. And those with 1: 9 pitch are made to have a better performance when projectiles of up to 73gr are used.
There is no guarantee that the armaments made in NATO 5.56x45mm will work properly if fired ammunition .223 Remington. These armaments are made to cycle safely when the chamber is under high pressures and heavier projectiles are used.
How dangerous and serious is it to shoot 5.56x45mm NATO ammunition at .223 Remington weapons? Dangerous enough for SAAMI, in the section “Combining Weapons and Unsafe Ammunition” from the book ” SAAMI Technical Correspondent’s Handbook “, to consider it unsafe, stating that “In weapons made in .223 Remington, do not use military ammunition 5.56x45mm BORN.”
ATK, an ammunition manufacturer that is part of the Federal and Speer group, has issued a bulletin entitled “The difference between Remington’s .223 and NATO Military 5.56x45mm,” and in this ATK attests that using 5.56x45mm NATO ammunition in armaments .223 Remington, can result in: “… gas leaks, exploded ammunition, exploded capsules and malfunctioning weaponry.”
ArmaLite does not think it is as dangerous as SAAMI and ATK say. In ArmaLite’s technical note # 74, they say that “millions of 5.56x45mm NATO ammunition were fired safely into Eagle Arms and ArmaLite armaments with cameras that have met SAAMI specifications for the past 22 years,” and had no catastrophic failure.
What does all this mean? If you operate a NATO 5.56x45mm rifle, you can shoot it with both ammunition at 5.56x45mm NATO and ammunition at .223 Remington safely. If the barrel pitch of your armament is 1: 7 “you should use ammunition with projectiles up to 60gr or heavier. If the pitch is 1:12 “you should use ammunition with projectiles lighter than 60gr. And if you use a weapon made for .223 Remington, you should NOT use 5.56x45mm ammunition of any kind.
5.56x45mm NATO weapons have a 1: 7 “or 1: 6” rationing step to stabilize long and heavy projectiles over long distances. Any weapon that has a 1: 7 “raid step will work best with projectiles up to 90gr.
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