Alex C. at The Firearm Blog documents what he claims is a similar mishap occurring in an FS2000 just two days ago.

I’m not sure that I buy the story, simply based on what I’ve seen when a 300BLK does detonate in an AR-15 also chambered for .223/5.56.

We posted a pair of stories last month about the near complete destruction of a high-end precision AR-15 that occurred when someone carelessly loaded a 300BLK cartridge into a magazine of 5.56 cartridges, handed to a shooter firing a .223 Wlyde chambered rifle (.223 Wylde is a chamber designed to fire .223 and 5.56 equally well that is popular among target shooters).

The result of the 300BLK in the .223 Wylde-chambered AR-15 was a catastrophic failure. The upper split and fragmented, the bolt carrier group split, etc. It was nothing short of a miracle that the shooter wasn’t seriously injured or killed. The kaboom resulted complete scrapping of the upper and all it’s associated parts except for the handguard, and the lower receiver and all of its parts except the stock and grip.

Most importantly to us, when the AR-15 fired, the 300BLK bullet was violently swaged (if “violent swaging” is a viable term) down the first few inches of the barrel, in addition to the damage it did when the cartridge detonated in the upper and lower receivers. The bullet could not be removed from the barrel, and the shooter still has a “bullseye” cross-section of the rifle barrel with bullet lodged inside it in his garage as a reminder.

The photos on TFB show an unobstructed barrel. Alex C asserts that the .30 bullet went all the way through a .223 barrel, and says they, “inspected the gun and could find nothing out of the ordinary.”

I simply don’t see how it could have happened. If a 300BLK fires in a 223 barrel, it is going to blow the gun up.

Feel free to tell me why I’m wrong in the comments.