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223 vs 556 Rifle Brass

Even the most experienced rifle owners can sometimes mistake the 233 ammo for the 556 rifle ammo. The main reason why many people make a mistake between these two cartridges is because of their similarity and vast amount of inaccurate information posted on the internet. Once something erroneous is posted on the Internet, it tends to be difficult to erase or determine the most accurate information.

The 223 cartridges are usually loaded with a .224-inch diameter designed with a weight that ranges between 35-80 grains. The two most widely available weights are the 55 and 62 grains, which respectively weigh 3.6 and 4.02 grams. The 556 is issued for military calibers.

What is the big deal between similar cartridges?

It is important to know the difference between these two ammunition types because if you make a mistake, the error can prove fatal.
What are the differences between the ammunition for the 223 and 556 calibers?
1. Dimensions: Physically the dimensions of the 223 and the 556 ammunitions are visually very similar and it is impossible to differentiate the two based on this observation alone.
2. Pressurization. In general, the 556 firing chamber tends to be less pressurized than the 223 chamber. In addition, the 223 ammunition is frequently loaded to a lower pressure than 556.
3. The 556 rifle chamber also does not have the same dimensions as the 223 chamber.
4. The 556 has a thicker wall so that it can handle higher pressures. The thickness also reduces the interior volume of the casing, which is smaller than that of a 223.
5. Some 556 loads tend to have slight increase in overall length than the load of the 223.

The biggest difference between the 223 and the 556 lies not in the cartridge but in the rifles. Both the 223 and 556 rounds will chamber in rifles designed for either cartridge, but the critical component is often different in each rifle.
Experts indicate that it is these subtle differences in the barrel that prevent the ammunition between these two to be completely interchangeable.

Safety Precautions with 223 vs 556 Ammunition

If you have rifles of both calibers, it may be easier and safer to always shoot 223 ammunition. With most modern rifles, the .223 Rem cartridges will safely shoot from any rifle chambered for the 223 or 556.

If you want to shoot .556 rounds, make sure that your rifle is designed for 556 ammunition; if you ever shoot 566 Military cartridges from a normal 223 rifle, expect something bad to happen from a simple malfunction to a possibly catastrophic failure. If you do own and regularly shoot both calibers, establish a process of keeping the ammo, magazines and accessories separated. Check box labels and headstamps regularly and default to 223 ammunition if in doubt. The biggest danger is in semi-automatic magazines being pre-loaded and not easily seeing the headstamps of the cartridges in the magazine.

Ultimately, the only way to ensure you are using the correct ammo is to check to see what's stamped on the barrel of your gun and to consult your owner's manual. Although these calibers are often used interchangeably, make sure that you only use ammo that has been approved by the firearm manufacturer for your particular gun.

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