The Difference Between .223 and 5.56

Are .223 and 5.56 interchangeable? 

When it comes to your primary rifle, a large number of them are chambered in 5.56 as this is a common, lightweight, and relatively cheap round that fits the most common rifle in the country, the AR-15. However, when you go to the gun store to pick up ammo, sometimes you may hear, “we’re all out of 5.56, but we have .223”). That being said, are 5.56 and .223 the same? Let’s take a moment and try to dissect differences between .223 and 5.56 NATO, and see if these rounds are truly interchangeable. There is a chance a lot of you are up to speed and that's fantastic. However, as far down the firearms road we may be, it's sometimes good to stop and help out the folks who are new and learning. We are going to dispel some myths that you may see on the internet forums, and make sure those who may be newer to firearms are given accurate information. Without getting into too much detail, here's the basics most people should know and I'll come right out and start with the point.

The Differences Between .223 and 5.56

To put it simply, there is ZERO difference between .223 & 5.56 NATO aside from pressure. The 5.56 NATO cartridge provides approx 6000 psi more than the .223 cartridge. 

Before you get all upset over that information being incorrect and there are different pressures for different bullets, I'm sure a lot of you are already yelling to me in your head and pouncing on the keyboard. I realize that if you pick up various brands of .223 and 5.56 that you'll have different measurements, different thicknesses, different volumes, and different overall lengths of the bullets themselves. And you be correct, however, those differences are just that, differences between BRANDS. 

Let’s break it down a bit further.

Chamber Length

The true difference is actually NOT in the cartridge itself, but rather in the rifle's chamber. A 5.56 NATO chamber has a longer throat than a .223. This design might not sound all that impressive, but it actually allows the chamber to handle the higher pressures of the 556 NATO cartridge. This design was also developed to avoid cases sticking in chambers and to avoid feeding issues for the military. A .223 is a lower pressure round that has actually been found to be more accurate than a 5.56 round, due to a tighter chamber tolerance and shorter throat. The 6000psi difference comes simply from a different powder and hotter load.

Then What is .223 Wylde?

While you are probably familiar with the .223 Remington round, what about .223 Wylde? Well, of course we can toss that one in the mix. The .223 Wylde is not actually a round, but instead is a chambering. was developed to achieve the best of both worlds; higher accuracy and higher pressure (equating to roughly 140-170 fps difference between the .223 and 5.56 rounds). That's right, .223 Wylde allows a shooter to fire .223 Remington and 5.56 NATO rounds out of the same barrel without losing any of that accuracy. 

So can a 5.56 Rifle Fire a .223 Round?

The question now is can a rifle that is chambered in 5.56 fire a .223 round, and vice versa? Well, since the only difference between the rounds is the pressure, yes a 5.56 firearm can fire .223 Remington.

Which Round Should You Use?

So if you are going to buy or build an AR15 style rifle, which round should you choose, .223 or 5.56? Well that's dependent on the purpose in my opinion. If precision (and I use that term loosely in regards to semi auto firearms, as they are not always the most accurate) is what you're after then using .223 Remington rounds is going to be your best option. If you'd like to shoot .223 and 5.56 without any issues. The 2.23 Wylde chamber is certainly a good option for you to choose. If the highest level possible of reliability in a large variety of ammo brands is your concern, then 556 is your go-to.

Wrap Up

Now that we have distinguished the differences between .223 and 5.56, the discussion of whether or not a semi-auto firearm is a precision firearm is a chat for another time. Hopefully this little blurb was helpful for some of you and perhaps it'll clear up some misinformation that's been flying around for quite a long time now.

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