Understanding 5.56x45 Ammo: An In-Depth Guide
The 5.56x45mm ammunition, often referred to as 5.56x45 ammo, is one of the most commonly used types for the AR-15 series rifle. This cartridge, which is a NATO standard round, has been adopted by various military forces, including the United States, for their M16 and M4 rifles.
Dimensions and Specifications
Unlike many other ammunition types, the nomenclature of 5.56x45 ammo uses the decimal point convention, where 5.56 represents the bullet diameter in millimeters and 45 represents the approximate length of the cartridge (starting from the neck to the bottom of the rim). It's important to note that this should not be confused with a multiplication, as the 'x' does not imply a mathematical operation.
To clarify, if you were to multiply .0394 by 5.56, the result would be approximately .219 inches; however, this is not the diameter of the bullet. The bullet actually measures approximately .224 inches in diameter, as measured by a certified micrometer. The '5.56mm' refers to the inside diameter of the barrel lands, which can be accurately measured using dial calipers or precision pin gauges for firearms with an odd number of lands.
Standard NATO Cartridge
The 5.56x45mm ammunition is part of the standard NATO set, which includes other popular calibers like the 9x19mm Parabellum and the 7.62x51mm NATO. This round is widely used in NATO standard assault rifles and squad automatic weapons (SAW's).
Bullet and Cartridge Specifications
Diameter of the Bullet: 5.56mm, measured across the lands (the ridges in the barrel). Length of the Cartridge Case: Approximately 45mm, which is the length of the cartridge case from the neck to the bottom of the rim. This is not the overall length of the cartridge, which includes the bullet.It's important to note that while the specification states the cartridge length as about 45mm, the length can vary slightly, especially in fired and reloaded ammunition. A new cartridge might be slightly longer than the designated length, but the discrepancy should not be significant.
Developing and Naming Ammunition Cartridges
When a new cartridge is developed, it is typically submitted to organizations such as the SAAMI (Sporting Arms and Ammunition Manufacturers' Institute) in the United States and CIP (Commission Internationale Permanente pour l'Eprouve des Armes a Feu Portatives) in Europe. These organizations ensure that the ammunition meets safety and performance standards.
The naming conventions for these cartridges are generally accepted, and terms like '5.56x45' or '5.56x45mm' are widely used, particularly in European classification systems. However, the naming can vary based on the specific requirements and usage in different regions.
Understanding the nuances and specifications of 5.56x45 ammunition is crucial for both enthusiasts and professionals in the firearms industry. Whether you're a collector, a hunter, or a military personnel, knowledge of the technical aspects ensures that you can operate your equipment safely and effectively.