5.56 vs. .223 Ammo: What You Should Know

There is a common misconception out there that 5.56x45mm NATO and .223 Remington are the same, or effectively the same, for all intents and purposes. Close on the heels of this misconception is the question, “Are 5.56 and .223 ammo interchangeable?” While these cartridges are extremely similar, they are not, in fact, the same. This post will break down the distinctions between them, and why it’s important to know them. 

Are 5.56 and .223 Ammo the Same?

If you put two FMJ 5.56 and .223 cartridges down next to each other on a table, standing them up on the cartridge base so you couldn’t see the headstamp, you would indeed think they are exactly the same.

Perhaps this is because the cartridge dimensions are, in fact, indistinguishable. One can also use the exact same bullets to load both casings - adding to the mystique.

But that is where the similarities end. The main difference between .223 and 5.56 ammo has to do with propellant charge. The 5.56 NATO cartridge is loaded to slightly higher chamber pressures. For the 5.56, it’s approximately 58,000 PSI whereas it’s about 55,000 PSI for the .223 Remington.

This differential in chamber pressures means that, while it could be considered safe to shoot a .223 cartridge in a 5.56 rifle, it is not safe to shoot a 5.56 cartridge in a .223 rifle.

The difference deepens with respect to chamber dimensions. A 5.56 chamber has a slightly longer chamber throat - .125” longer, to be precise.

This difference in chamber dimensions further complicates chamber pressures. Were one to attempt to shoot a 5.56 cartridge in a .223 chamber, the pressure spike would potentially damage the rifle - if not causing the primer to back out of the cartridge, or worse.

And while a .223 cartridge could in theory be fired from a 5.56 chamber, it’s not necessarily advisable. The longer 5.56 chamber throat would prevent the cartridge from attaining its intended chamber pressures, sacrificing performance and potentially adversely affecting cycling.

Of course, the long and short of this is that these two cartridges are not the same, and that you should stick with firing only the exact cartridge in your gun that’s indicated by the barrel stamp.

There is one more difference between these two cartridges; 5.56 cartridges are normally manufactured with a crimped primer pocket that helps prevent the primer from backing out during semi-auto or full-auto firing, whereas .223 Remington cartridges typically feature uncrimped primer pockets. 

What Are 5.56 and .223 Ammo Good for?

Despite the fact that 5.56 and .223 are not exactly the same cartridge, they produce very similar ballistic performance and are suitable for the same shooting disciplines. Among these are as follows:

• Training and drilling: Because both 5.56 and .223 ammo produce such low recoil and are such affordable cartridges, they are extremely popular for training and drilling. These are also two of the best centerfire cartridges for introducing new shooters to the shooting sports because of these reasons. 
• High-volume target shooting: Because both 5.56 and .223 are low-cost, they are excellent options for plinking, range therapy, or just burning brass for fun at the range.
• Long-range shooting: Both 5.56 and .223 ammo produce fairly high ballistic coefficients and are very fast, flat-shooting cartridges shooting a light bullet. While there are other better cartridges with respect to wind drift, the drop scores of 5.56 and .223 are pretty impressive and for such a small cartridge, it is one of the best out there for long-range shooting. 
• Defensive applications: While there are some concerns with overpenetration with such a small, fast bullet, when loaded appropriately, either of these cartridges could be viable for defensive applications. 
• Small game hunting and other sporting applications: Highly affordable, widely available, low on recoil, and high on dispatching power, both .223 and 5.56 can be used for small and medium game hunting, with some preferring them for predator control purposes. 

All in all, these are among the most versatile rifle cartridges on the market and can be adapted to a wide range of shooting disciplines. 

Stock Up on 5.56 and .223 Ammo Here

Whether you’re here for 5.56 or bulk .223 ammo, we have what you need and represent the top brands in both cartridges. Shop our collections of 5.56 and .223 ammo and stock up your ammo cans so you’re ready for your next range day.