Estimated reading time: 7 minutes
If you spend enough time around AR-15s I’m sure you heard about .223 Wylde. The .223 Wylde is not a caliber like the .223 Remington and the 5.56x45mm NATO cartridges, but a chamber specifically designed to shoot both the .223 and 5.56. In the 1990s, the .223 Wylde chamber was designed to accurize the 5.56 NATO for NRA High Power rifle competitions.
The designer, Bill Wylde, modified the chamber using dimensions from both the 5.56 and .223. Wylde basically found a sweet spot in the chamber dimensions to wring out the best accuracy in both 5.56 and .223 cartridges without creating excessive pressure. You do know that the 5.56 and .223 are different cartridges, right?
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.223 Rem vs 5.56 NATO
Back in 1957, the .223 Remington was an experimental cartridge being developed in conjunction with the AR15 rifle. One of the US Military’s requirements for the new cartridge was the cartridge’s projectile needed to have a velocity equal or better to the speed of sound at 500 yards.
The US Military adopted the new .223 Remington with a 55-grain FMJ bullet and a muzzle velocity of 3,250 fps, and officially called it Cartridge, 5.56 mm ball, M193. The then new M16, a full auto version of the AR15, and the then new cartridge literally were baptized in combat in the late 1960s during the Vietnam War.
Soon after the Military adoption the new cartridge, Remington submitted the .223 Remington caliber to SAAMI and after SAAMI’s blessing, Remington introduced the .223 Remington to the commercial market in December 1963.
The chamber pressure is different, too. The .223 Remington produces 55,000 psi (Pounds per Square Inch) while the 5.56×45 NATO produce 62,300 psi. What this boils down to is the 5.56 runs a lot hotter than .223.
The Main External Differences
Externally, the dimensions of the 5.56 NATO and .223 Remington cartridges are the same. The difference in the two cartridges and chambers occurred in the late 1970s when FN Herstal was developing a version of the 5.56 caliber for NATO adoption. In October of 1980 there was a change. NATO adopted the FN-designed SS109 cartridge with a 62-grain boattail bullet with a muzzle velocity of 3,100 fps. The US Military called this load the M855, and this established the 5.56×45 NATO name.
It’s common for a lot of shooters to think the 5.56×45 NATO is interchangeable with the .223 Remington. It’s the chamber dimensions that differ between the .223 Remington and the 5.56×45 NATO. The 5.56×45 NATO chamber has a longer throat than the .223 Remington chamber. The chamber throat is the area forward of the cartridge chamber that provides clearance for the bullet in the cartridge. This is also known as freebore.
Freebore
Freebore diameter is larger than the groove diameter of the rifling to allow the bullet to jump from the cartridge case mouth through the freebore and into the leade and rifling. A .223 chamber also differs because it has a steeper leade. Leade is the angle cut into the rifling the allows the bullet to enter the rifling with minimal damage. It funnels the bullet into the rifling. This gives the .223 more precision and accuracy, something that is not required in a combat rifle. Sure it needs to be accurate but not as accurate as a target rifle or varmint rifle. Enemy combatants are typically taller than coyotes.
Since the 5.56 is a military load and the military wants to use heavier and longer bullets in all types of environmental conditions, the throat or freebore is roughly .125 inches longer on a 5.56 chamber than the .223 Remington. The .223 chamber has a throat length of .040 inches and throat diameter of .2240 inches, the 5.56 throat measures .070 inches and the throat diameter is .2265 inches. The leade angle on the .223 is 3 degrees, 10 minutes and the 5.56 is 1 degree 20 minutes.
The .223 Wylde chamber has a leade angle of 1 degree, 15 minutes and a throat length of .078 inches and throat diameter of .2242 inches. Mr. Wylde decided to use the freebore diameter of the .223 and the leade angle of the 5.56. The throat length or freebore is longer than either the .233 and the 5.56. This means a .223 Wylde chamber stabilizes the bullet better with no excessive pressure. Kind a win-win for anyone who shoots .223 and 5.56 ammo.
Can You Shoot 5.56 in a .223 Rifle?
If you are wondering what cartridge is safe to shoot in what chamber a good guideline to use is this: .223 Remington ammo is safe to shoot in a .223 Remington, 5.56×45 NATO, and .223 Wylde chamber, but 5.56×45 NATO ammo should only be shot in 5.56×45 NATO or .223 Wylde chambers. Not that shooting 5.56 ammo in .223 chamber will split your barrel back like a banana peel, most rifles can tolerate the increase in pressure. But 5.56 NATO ammo will create more pressure when fired out of a .223 chamber.
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Do You Need A .223 Wylde Chamber?
Short answer is yes. Not because you are going to see jaw-dropping accuracy. That depends on the rest of your rifle setup, the ammo you shoot, and your ability. But if punching clusters of holes is your thing, the 223 Wylde is your option. When it comes to AR15 rifle manufacturers the 5.56 NATO and 223 Wylde chamber are the most common. Chances are if you have a newer AR15, the barrel will be stamped: .223 Wylde.
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Why would any manufacturer not want to use a more accurate chamber? The cost to cut is the same, right?