I was reading up on the .223 round and saw a article from a instructor about making sure your AR 15 is chambered for 5.56 not .223 Rem. What is a new Bushmaster chambered in ? Is this really a problem? I notice my Wolf ammo says .223 on the box and nothing about 5.56. The article was written by Jeff Chudwin Olympia Fields P.D See part of the article.....................................

"If you choose to go the AR-15 type system route, be certain that the weapon manufacturer has the chamber cut to the military 5.56 m/m dimension, not the civilian .223 Remington chamber. There is a difference in chamber length that can cause military length cartridges fired in shorter .223 chambers to blow primers out of the case, disabling the gun. In our classes, we have seen this on a number of occasions."

Bushmaster chambers are 5.56.

FWIW, any reading or perusing of Bushmaster's web-site would give you this info.
Ammo Fac at top of ammunition forum covers this topic too.

Mike

I do believe their DCM Models are chambered for .223.  The other rifles/carbines are Mil Spec and chambered for 5.56.  Check the barrel, it should be stamped.

The Bushmaster DCM and Varminter are .223, and maybe their new stainless steel barrel? All others are 5.56.

If you have a gun chambered in 5.56, it is ok to shoot both 5.56 and .223 ammo without a second thought.

If you have a gun chambered in .223, you can shoot .223, but shooting 5.56 *may* cause you problems. Nothing catastrophic, but *maybe* some blown primers or other jams.

Quoted: The Bushmaster DCM and Varminter are .223, and maybe their new stainless steel barrel? All others are 5.56. If you have a gun chambered in 5.56, it is ok to shoot both 5.56 and .223 ammo without a second thought. If you have a gun chambered in .223, you can shoot .223, but shooting 5.56 *may* cause you problems. Nothing catastrophic, but *maybe* some blown primers or other jams.

For that reason, I once chose the Colt Accurized Rifle (CAR-15, 5.56) over some of the discussed choices.
Probably a mistake for the CR6724 was never considered anything amazing in the accuracy catagory.

Checking my lower it is marked Cal .223-5.56mm.

Your lower may not correctly reflect your barrel's actual chamber.

Check your barrel, on top in front of your front sight.