5.56 NATO vs .223 Remington: What Every AR-15 Owner Needs to Know
The difference between 5.56 NATO and .223 Remington is one of the most misunderstood topics in the AR-15 community. While these cartridges look identical and are often used interchangeably, the distinction matters for safety, accuracy, and cost. Understanding the differences will help you make informed decisions about ammunition, barrels, and reloading.
Chamber Pressure: The Critical Difference
The fundamental difference between these cartridges is pressure. 5.56 NATO is loaded to a maximum average pressure (MAP) of 62,366 PSI, while .223 Remington is loaded to 55,000 PSI. This 7,000+ PSI difference creates the entire safety equation. When you fire 5.56 NATO ammunition in a .223 Remington chamber, the higher pressure can cause bolt carrier group acceleration, increased wear, and potential safety issues. Conversely, .223 Remington ammo in a 5.56 chamber will function fine but won’t be optimized for that chamber.
Chamber Dimensions and Leade
5.56 NATO and .223 Remington chambers have slightly different dimensions, particularly in the throat area (leade). 5.56 NATO chambers have a longer leade to accommodate tolerance stacks in military ammunition, while .223 Remington chambers are tighter. This difference allows 5.56 to safely handle hotter ammunition. If you fire 5.56 rounds in a tight .223 Remington chamber, the bullet may engrave more aggressively on entry, creating higher pressure spikes.
The .223 Wylde Solution
.223 Wylde chambers offer the best of both worlds. Designed by firearms engineer Bill Wylde, this chamber accepts both 5.56 NATO and .223 Remington safely. It combines the .223 Remington’s tighter dimensions with a 5.56 NATO-length leade. This design allows you to shoot either ammunition type while maintaining optimal accuracy and safety. Many precision shooters prefer .223 Wylde chambers because they provide better accuracy than 5.56 NATO chambers while remaining fully compatible with NATO ammunition.
Practical Considerations for AR-15 Owners
If you own a 5.56 NATO chambered rifle, you can safely shoot .223 Remington ammunition. If you own a .223 Remington chamber, avoid 5.56 NATO ammunition. The risk isn’t theoretical—extended use of hotter ammunition in a tight chamber can cause bolt carrier group battering, increased extraction forces, and potentially dangerous pressure signs. When selecting an AR-15, specify your intended use. If you plan to shoot surplus military ammunition or want flexibility, choose 5.56 NATO. If you want maximum accuracy and plan to source commercial ammunition exclusively, .223 Remington or .223 Wylde both work well.
Ammunition Cost and Availability
5.56 NATO ammunition is typically less expensive due to military manufacturing and surplus availability. Commercial .223 Remington tends to be slightly pricier but offers tighter quality control from manufacturers like Federal, Hornady, and Speer. If cost is a major factor, 5.56 NATO rifles give you more options, though current market conditions affect availability significantly.
For Handloaders
If you reload, the distinction becomes academic—you control pressure and performance. However, understanding chamber type remains important. .223 Wylde chambers are ideal for handloaders because they enable the most consistent velocity and accuracy with both smaller and larger bullets. Most precision reloaders using .223 components prefer .223 Wylde chambers because the tighter dimensions reduce bullet runout variation.
Making Your Choice
For a first AR-15, specify 5.56 NATO unless you have a specific reason for .223 Remington. You’ll have more ammunition options, lower costs, and the ability to use surplus or commercial ammunition without hesitation. If you’re building a precision rifle or competition firearm, .223 Wylde offers the flexibility and accuracy advantages that serious shooters appreciate. Either way, knowing your chamber type prevents dangerous ammunition selection mistakes and ensures your rifle performs as intended.
