Will .223 Remington be accurate in a 5.56 NATO rifle?

It depends on the rifle. The longer throat of a 5.56 chamber can cause a slight accuracy reduction with .223 ammunition because the bullet must jump further before engaging the rifling. For practical shooting, the difference is minor. For precision work, a .223 Wylde or dedicated .223 chamber is preferable.

Can I Shoot .223 Remington in a 5.56 NATO Chamber?

Q: Can I shoot .223 Remington in a 5.56 NATO chamber?

Yes. Shooting .223 Remington in a 5.56 NATO chamber is generally safe. .223 operates at lower pressure and uses less case capacity. The longer 5.56 throat may reduce accuracy slightly, but there is no pressure safety concern.

Why It Works

Lower Pressure, More Throat Room

.223 Remington is a SAAMI-standardized cartridge with a maximum average pressure of 55,000 psi. The 5.56 NATO chamber is designed for ammunition that runs at approximately 58,000 psi (NATO EPVAT method). Firing the lower-pressure .223 Rem round in a chamber rated for the higher-pressure 5.56 NATO presents no overpressure risk.

The 5.56 NATO chamber also has a longer leade — approximately 0.162 inches versus about 0.085 inches in a standard .223 Rem chamber. When you fire .223 Rem in a 5.56 NATO chamber, the bullet travels a longer distance before engaging the rifling. This is the opposite of the problem that makes 5.56 in a .223 chamber risky.

The Trade-Off

The Accuracy Question

The longer jump from case mouth to rifling in a 5.56 NATO chamber means .223 Rem ammunition is not being fired with the bullet already in contact with the lands — the bullet is slightly loose before it engages. This is called "bullet jump."

For practical shooting — defensive use, hunting, most competition — the difference is negligible. At longer ranges and in precision rifle contexts, it can open up groups modestly. How much depends on the specific bullet, its ogive shape, and how the load was designed.

For match-grade precision work: A .223 Wylde chamber is optimized for exactly this — it accepts both cartridges while tightening the bore dimensions for accuracy. Many AR-15 builders use .223 Wylde barrels specifically because they handle both without the accuracy compromise.

Specification	.223 Remington	5.56×45mm NATO
Max Pressure	55,000 psi (SAAMI)	~58,000 psi (NATO EPVAT)
Leade Length	~0.085 in	~0.162 in
Case Length	1.760 in	1.760 in
Overall Length	2.260 in max	2.260 in max

Practical Use

When Shooters Do This

Shooting .223 Rem in a 5.56 NATO rifle is a common practice. Many shooters own 5.56 NATO-chambered AR-15s and buy .223 Remington ammunition because it's widely available and sometimes cheaper, particularly in certain bullet weights and match configurations.

Commercial .223 Rem ammunition is also more likely to be loaded to tighter SAAMI tolerances with consistent bullet seating — which can actually improve accuracy in some rifles versus mixed military surplus 5.56.

The reverse is not the same: Shooting 5.56 NATO in a .223 Remington chamber carries real risk. See the companion page for that direction: Can I shoot 5.56 in a .223 chamber?

Bottom Line

Safe to shoot .223 Remington in a 5.56 NATO chamber. You may see minor accuracy differences at long range. For precision shooting, a .223 Wylde barrel is the better tool.