Understanding the difference between 223 Remington and 5.56x45 NATO ammo is something that can confuse even the most experienced rifle owners. This can largely be attributed to the prevalence of incorrect 5.56 vs 223 information that has been published on the web in the last two decades.

The problem is that a lot of this information is presented as factual when it couldn't be further from the truth. Unfortunately this information is often regurgitated by others as fact which leads to even more misinformation. So what's the real difference between 223 and 556 ammo, and which can be used in your rifle? Continue reading to find out!

Here are a few facts when it comes to 223 Rem. vs 5.56 ammo.

• Physical dimensions of 223 Remington and 556 ammo are practically identical.
• Typically, 5.56 chambers will be less pressurized than their 223 chamber counterparts. 556 ammunition is often loaded to higher pressure than its 223 counterpart.
• 5.56mm rifle chambers do not have the same dimensions as .223 chambers - it is this difference in critical areas of the barrel that prevent these ammunition types from being completely interchangeable.

What's the difference between 223 Remington and 5.56x45 ammo?

Knowing those facts, what is the real difference between 223 and 5.56 ammo? To understand the difference between them, it is obviously important to understand what each ammo type actually is. After all, you can't compare two things if you don't understand both individually.

What is 223 Rem. ammo?

223 Ammo is essentially slang for the 223 Remington cartridge, and as we mentioned, it does share nearly identical external dimensions with the 5.56 cartridges. Let's take a look at some facts about 223 cartridges:

• They are loaded with .224 inch diameter bullet.
• Weights range between 35 to 80 grains, with the most common varieties being 55 and 62 grain which weigh in at 3.6 and 4.02 grams.

What is 5.56 NATO Ammo?

5.56 ammo is essentially 5.56mm NATO. NATO is responsible for creating standards for military issued calibers.

A lot of ammunition manufacturers will imply that these calibers can be used interchangeably. While that is sometimes true, it requires expert knowledge and if you do not know what you are doing can be extremely dangerous if not fatal.

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, if you do not know what you are doing you

Summary:

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 manufacturer of your firearm.