History
The development of the cartridge, which eventually became the .223 Remington, was 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 (CONARC). Development began in 1957. A project to create a small-caliber, high-velocity (SCHV) firearm was created.Cartridge dimensions
The .223 Remington has a 28.8- grain H2O (1.87 ml) cartridge case capacity. .223 Remington maximum CIP cartridge dimensions. All sizes in millimeters (mm). Americans would define the shoulder angle at alpha/2 = 23 degrees. The common rifling twist rate for this cartridge is 305 mm (1 in 12 in), 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 (2016) 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..223 Remington vs. 5.56×45mm NATO
In 1980, the .223 Remington was transformed into a new cartridge and designated 5.56×45mm NATO (SS109 or M855).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 (case capacities have been observed to vary by as much as 2.6 grains (0.17 ml)), 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 hand-loaded, 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
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 1:9.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 Remington chambers are designed for. NATO chose a 178-mm (1-in-7) rifling twist rate for the 5.56×45mm NATO chambering. The SS109/M855 5.56×45mm NATO ball cartridge requires a 228 mm (1-in-9) twist rate, while adequately stabilizing the longer NATO L110/M856 5.56×45mm NATO tracer projectile requires an even faster 178 mm (1-in-7) 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 the 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. As the chambers differ accordingly the head space gauges used for the two chamberings differ. 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 (which is a similar occurrence with regard to pressure). 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: 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 shorter barrel yields a lower one. The first AR-15 rifles used a barrel length of 20". In the case of the 223 Remington (M193), ammunition loses or gains about 25.7 ft/sec for each inch of barrel length, while 5.56×45 mm NATO (M855) 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 (5.7 mm) diameter jacketed bullets, with weights ranging from 35 to 85 grains (2.27 to 5.8 g), with the most common loading by far being 55 gr (3.6 g). Ninety-grain and 95-grain Sierra Matchking bullets are available for reloaders.See also
* .30 RAR * 5 mm caliber * 6×45mm * Delta L problem *References
External links