.223 Remington
The .223 Remington is a rifle cartridge, developed in 1957 as a commercial hunting bullet for small mid-western varmint. Used as a test round for the ArmaLite's newer combat rifle in 1964, the ArmaLite AR-15 was adopted by the United States Army as the M16 rifle, The military version of the cartridge uses a 55-gr full metal jacket bullet and was designated M193. In 1980, the.223 Remington was transformed into a new cartridge, a 62-gr full metal jacket bullet with a 7-gr steel core for better penetration and designated 5.56×45mm NATO.
History
The development of the cartridge, which eventually became the.223 Remington, was intrinsically linked to the development of a new lightweight combat rifle. The cartridge and rifle were developed by Fairchild Industries, Remington Arms, and several engineers working toward a goal developed by U.S. Continental Army Command. Early development work began in 1957. A project to create a small-caliber, high-velocity firearm was created. Eugene Stoner of ArmaLite was invited to scale down the AR-10 design. Winchester was also invited to participate. The parameters requested by CONARC were:
- .22 caliber
- Bullet exceeding supersonic speed at 500 yards
- Rifle weight 6 lbs
- Magazine capacity of 20 rounds
- Select fire for both semiautomatic and fully automatic use
- Penetration of US steel helmet one side, at 500 yards
- Penetration of.135" steel plate at 500 yards
- Accuracy and ballistics equal to M2 ball ammunition
Eugene Stoner of ArmaLite had been advised to produce a scaled-down version of the 7.62×51mm NATO AR-10 design. In May 1957, Stoner gave a live-fire demonstration of the prototype of the ArmaLite AR-15 for General Wyman. As a result, CONARC ordered rifles to test. Stoner and Sierra Bullet's Frank Snow began work on the.222 Remington cartridge. Using a ballistic calculator, they determined that a 55-grain bullet would have to be fired at 3,300 ft/s to achieve the 500-yard performance necessary.
Robert Hutton started development of a powder load to reach the 3,300 ft/s goal. He used DuPont IMR4198, IMR3031, and an Olin powder to work up loads. Testing was done with a Remington 722 rifle with a 22" Apex barrel. During a public demonstration, the round successfully penetrated the US steel helmet as required, but testing showed chamber pressures to be excessively high.
Stoner contacted both Winchester and Remington about increasing the case capacity. Remington created a larger cartridge called the.222 Special. This cartridge is loaded with DuPont IMR4475 powder.
During parallel testing of the T44E4 and the ArmaLite AR-15 in 1958, the T44E4 experienced 16 failures per 1,000 rounds fired compared to 6.1 for the ArmaLite AR-15. Because of several different.222 caliber cartridges that were being developed for the SCHV project, the.222 Special was renamed.223 Remington. In May 1959, a report was produced stating that five- to seven-man squads armed with ArmaLite AR-15 rifles have a higher hit probability than 11-man squads armed with the M-14 rifle. At an Independence Day picnic, Air Force General Curtis Le May tested the ArmaLite AR-15 and was very impressed with it. He ordered a number of them to replace M2 carbines that were in use by the Air Force. In November of that year, testing at Aberdeen Proving Ground showed the ArmaLite AR-15 failure rate had declined to 2.5/1,000, resulting in the ArmaLite AR-15 being approved for trials.
In 1961, a marksmanship testing compared the AR-15 and M-14; 43 % of ArmaLite AR-15 shooters achieved Expert, while only 22 % of M-14 rifle shooters did. Le May ordered 80,000 rifles. In July 1962, operational testing ended with a recommendation for adoption of the ArmaLite AR-15 rifle chambered in.223 Remington.
In September 1963, the.223 Remington cartridge was officially accepted and named "Cartridge, 5.56 mm ball, M193". The following year, the ArmaLite AR-15 was adopted by the United States Army as the M16 rifle and it would later become the standard U.S. military rifle. The specification included a Remington-designed bullet and the use of IMR4475 powder, which resulted in a muzzle velocity of 3,250 ft/s and a chamber pressure of 52,000 psi.
In the spring of 1962, Remington submitted the specifications of the.223 Remington to the Sporting Arms and Ammunition Manufacturers' Institute. In December 1963, Remington introduced its first rifle chambered for.223 Remington a Model 760 rifle.
Cartridge dimensions
The.223 Remington has a 28.8-grain cartridge case capacity..223 Remington maximum CIP cartridge dimensions. All sizes in millimeters.
Americans would define the shoulder angle at alpha/2 = 23 degrees. The common rifling twist rate for this cartridge is 305 mm, 6 grooves, Ø lands =, Ø grooves =, land width = and the primer type is small rifle.
According to the official CIP rulings, the.223 Remington can handle up to Pmax piezo pressure. In CIP-regulated countries, every rifle cartridge combination has to be proofed at 125% of this maximum CIP pressure to certify for sale to consumers.
This means that.223 Remington chambered arms in CIP-regulated countries are currently proof tested at PE piezo pressure. This is equal to the NATO maximum service pressure guideline for the 5.56×45mm NATO cartridge.
The SAAMI pressure limit for the.223 Remington is set at, piezo pressure. Remington submitted.223 Remington specifications to SAAMI in 1964. The original diagrams use English Inch measurements.
.223 Remington vs. 5.56×45mm NATO
In 1980, the.223 Remington was transformed into a new cartridge and designated 5.56×45mm NATO. This new round uses a 62-gr full metal jacket bullet with a 7-grain steel core for better penetration against lightly armored targets, specifically to meet the NATO requirement that the bullet be able to penetrate through one side of a WWII U.S. M1 helmet at 800 m. It had a slightly lower muzzle velocity than its predecessor, but better long-range performance due to higher sectional density and a superior drag coefficient. This requirement made the 5.56mm NATO round less capable of fragmentation than the.223 Remington and was considered more humane.Dimensions
The external dimensional specifications of.223 Remington and 5.56×45mm NATO brass cases are nearly identical. The cases tend to have similar case capacity when measured, although the shoulder profile and neck length are not the same and 5.56×45mm NATO cartridge cases tend be slightly thicker to accommodate higher chamber pressures. When handloaded, care is taken to look for pressure signs as 5.56×45mm NATO cases may produce higher pressures with the same type of powder and bullet as compared to.223 Remington cases. Sierra provides separate loading sections for.223 Remington and 5.56×45mm NATO and also recommends different loads for bolt-action rifles as compared to semiautomatic rifles.Rifling
is expressed as a ratio. A 1 in 12" ratio means that rifling is cut so that the bullet rotates 360° after having traveled 12 in. This is expressed as 1:12 spoken as 1 in 12 inches. Rifling must match the bullet design, which a shooter intends to use, to maintain accuracy.Many AR type rifles use 1:9, which is suitable for bullets up to or 1:7, which is suitable for bullets up to. Many AR rifle owners choose to build their own rifles, which is facilitated by a huge variety of barrels and other components. The custom-built ARs may have a barrel from 7.5 in to as long as 24 if used in varmint rifles primarily, often with Wylde or Noveske chambering.
The Sturm, Ruger & Co. AR-556 has rifling at 1:8. Their Mini-14 rifles have rates of 1:9. Ruger's American bolt-action rifle is also in 1:8. Smith and Wesson in their M&P15 also uses 1:7. The 5.56 mm NATO chamber will shoot either 5.56×45mm NATO or.223 Remington and is used by most makers of complete rifles and components.
Pressures
Remington submitted the specifications for the.223 Remington cartridge in 1964 to SAAMI. The original pressure for the.223 Remington was 52,000 psi with DuPont IMR Powder. The current pressure of resulted from the change from IMR to Olin Ball powder. The official name for.223 Remington in the US Army is cartridge 5.56 x 45mm ball, M193. If a 5.56×45mm NATO cartridge is loaded into a chamber intended to use.223 Remington, the bullet will be in contact with the rifling and the forcing cone is very tight. This generates a much higher pressure than.223 chambers are designed for. NATO chose a 178-mm rifling twist rate for the 5.56×45mm NATO chambering. The SS109/M855 5.56×45mm NATO ball cartridge requires a 228 mm twist rate, while adequately stabilizing the longer NATO L110/M856 5.56×45mm NATO tracer projectile requires an even faster 178 mm twist rate.Chambers
The.223 Remington and 5.56×45mm NATO barrel chamberings are not the same. While the cartridges are identical other than powder load, bullet weight, and chamber pressure, a significant difference is in barrel of the rifle to be used, not in the cartridge. The 5.56×45mm NATO chambers are dimensionally larger in certain critical areas than.223 Remington chambers. The chamber leades of the barrels of these rifles differ between designs.The leade is the distance from the projectile while seated in the case to the rifling, which is typically shorter in.223 Remington commercial chambers. Because of this, a cartridge loaded to generate 5.56×45mm NATO pressures in a 5.56×45mm NATO chamber may develop pressures that exceed SAAMI limits for.223 Remington when fired from a short-leade.223 Remington chamber.
The throating issue exists because in the US, having short chambers so that the bullet is being engaged at the moment of insertion has been traditional. European practice has more of a forcing cone construction, which can, by itself, allow significantly higher chamber pressure. All SIG Sauer handguns have European throating and all are certified to fire +P ammunition. Short throating and unnoticed bullet setback can easily increase chamber pressures by more than 10,000 psi.
By observation, 5.56×45mm NATO ammunition is not as accurate as.223 Remington in many of the AR type rifles extant, even with the same bullet weight. The.223 Wylde chamber specification developed by Bill Wylde solves this problem by using the external dimensions and lead angle as found in the military 5.56×45mm NATO cartridge and the 0.224 inch freebore diameter as found in the civilian SAAMI.223 Remington cartridge. It was designed to increase the accuracy of 5.56×45mm NATO ammunition to that of.223 Remington. Other companies also have chamber designs that increase 5.56×45mm NATO accuracy.
Comparisons
The table contains some estimated pressures based on normal proofing practice and on the known increases in pressure caused by bullet setback. The proof pressure of M197 is 70,000 psi.The following table shows the differences in nomenclature, rifling, throating, and normal, maximum, and safe pressures:
| Cartridge | US designation | NATO designation | Bullet | Rifling | Throat | Pressure in NATO chamber | in.223 SAAMI chamber | Safe sustained |
| .223 Remington | .223 Rem | 55gr FMJ | 1:14 | tight | Yes | |||
| .223 Remington | M193 | 5.56×45mm | 55gr FMJ | 1:12 | tight | Yes | ||
| .223 Remington | M197 | C10524197-56-2 | 1:12 | tight | One time only | |||
| 5.56×45 mm NATO | M855 | SS109 | 62 gr ball | 1:7 | long | EPVAT | over | No |
| 5.56×45 mm NATO | M856 | L110 | 77gr Tracer | 1:7 | long | EPVAT | over | No |
| 5.56×45 mm NATO | M857 | SS111 | Tungsten carbide | 1:7 | long | EPVAT | over | No |
| 5.56×45 mm NATO | Proof | Proof | unknown | 1:7 | long | EPVAT | estimated | No |
Beside the NATO EPVAT testing pressure testing protocols the other employed peak pressure measurement methodology or methodologies to correlate this table remain unknown.
Effects of barrel length on velocity
Barrel length helps determine a specific cartridge's muzzle velocity. A longer barrel typically yields a greater muzzle velocity, while a short barrel yields a lower one. The first AR-15 rifles used a barrel length of 20". In the case of the.223 Remington, ammunition loses or gains about 25.7 ft/sec for each inch of barrel length, while 5.56×45 mm NATO loses or gains 30.3 ft/sec per inch of barrel length.Usage and commercial offerings
The.223 Remington has become one of the most popular cartridges and is currently used in a wide range of semiautomatic and manual-action rifles and even handguns, such as the Colt AR-15, Ruger Mini-14, Remington Model 700, Remington XP-100, etc. The popularity of.223 Remington is so great, that in the US it virtually eliminated all other similar.22 caliber center-fire varmint rifle cartridges.It is commercially loaded with 0.224-inch diameter jacketed bullets, with weights ranging from 35 to 85 grains, with the most common loading by far being 55 gr. Ninety- and 95-grain Sierra Matchking bullets are available for reloaders.