This article is a little different from other gunsmithing tips and procedures. Since I have seen at least 3 returns come in with this problem I think a warning is in order.

It can not be stressed enough to match your ammunition to the markings on the barrel!

The following are photos of a rifle returned for a catastrophic failure due to firing a round of .300 Blackout in a rifle chambered for 5.56/.223
I want people to be aware of this as I have had more than one rifle returned for this type of failure. It’s usually when someone at the range has a 5.56 caliber rifle and they are next to someone that has a .300 Blackout. A round of .300 Blackout gets mixed in with some .223 on the shooting bench and disaster follows. Always pay close attention to the rounds you are loading in your magazine, and never let ammunitions get mixed together on the shooting bench. Don’t let this happen to you!

As you can see in this sectioned barrel the bullet actually gets squeezed down to the smaller bore size and the overpressure makes the gun explode. In this case the lead actually shot out of the middle of the jacket. I have also seen a 110 grain .300 blackout bullet get knocked out of the bore intact after the rifle failed. It ended up being a slug that was .22 caliber, about 1 ½” long and 110 grains.

If you ever have questions about your rifle, you are always welcome to call Windham Weaponry Customer Service (Toll Free: 1-855-808-1888). Shoot Safely!