Neighbor’s son called me just now. He’s in his early 20’s. He was hoping to use my range to check out his rifle, but I’m not taking any visitors when it’s supper time and we’re having steak. I asked if he wanted to check the sights, and that was his intent. He has a new 300 BO that has been repaired. He shot it recently and he said it blew up. Chambered for 300 BO, but the barrel was 5.56. Yep, it blew up.

He said the seller (I don’t know who that was...yet) repaired the rifle and gave him a bunch of free stuff. No kidding.

Said he had some minor cuts and scuffs from the blow up.

Wait so .22 barrel with 300 BO camber?

You know you can chamber a 300BLK in a 223 chamber, right? Is he sure that he had a 300BLK?

He said he bought a 300 BO, which is what he asked them to build. Fired off a round of 300 BO in it and it blew up. 30 cal bullet in a 24 cal barrel. That’s all the info I have so far. And he said they “fixed it” after the blow up, which suggests that they know they messed up. Like I said, I don’t yet know who “they” are, but I will find out.

He is an Aggie, if that factors in. And he’ll bring the gun over here week after next and won’t shoot it till then. I’ll be on the other side of my tractor when he cranks off that first round.

Lol. You might want to look at the barrel before he shoots it again.

I think I would be checking everything on the rifle, ya just don't know nowadays.

I'd hire a lawyer before I worried about shooting a "repaired" rifle again

I don't know how you would chamber a 5.56 bbl with a 300 reamer, the reamer pilot won't go in the .224" bore???

My bet is he had a 5.56 bbl that got marked 300 Blackout. As unclebubba said a 300BLK will chamber and fire in a 5.56, you just get a ka-boom !!! Unfortunately we have had this happen with our bbls/guns way too many times......

This is another advantage of the 300 HAM'R over the 300 Blackout, it won't chamber or fire in any of the following sub .30cal chambers:

.204 Ruger
.223/5.56
.224 Valkyrie
.22 Nosler
6mm ARC
6.5 Grendel
6.8 SPC

I reckon that must be what happened - the wrong barrel or mismarked barrel. What I wonder is what actually happens when it goes Boom. What gets destroyed? I assume that most of the blast goes out the ejection port and the mag well, and hopefully that’s enough to keep the receiver from being dismantled.

It normally destroys the bbl, BCG and upper receiver, it's a pretty catastrophic boom based on the damage we see !!! We basically replace everything on the top end except the handguard, gas block and muzzle device when we repair them.

He's lucky he didn't lose an eye.

The guy came over this evening, with the previously blown up AR. It looked fine now, after being redone. It seems the problem was that a 5.56 barrel was mislabeled as a 300 BO. Tomorrow morning he’ll come over with the GF and we’ll shoot a bit.

I would check and recheck that one over. Just saying...

After I wrote yesterday’s comment, it occurred to me that when I looked at the rifle yesterday I didn’t see any markings at all about caliber. If he shows up to shoot this morning, I will check bore diameter and check to see if the caliber is marked anywhere on the AR. And there was no manufacturer’s name on the lower, at least not that I noticed.

Yeah....if is was a .223 barrel labeled .300, I'd be expecting something more than a "fix" from that manufacturer. That is a seriously good way to end up needing plastic surgery or a prosthetic eye. And with how things are manufactured, there is virtually NO chance they only made that mistake on one gun/ barrel.

The kid’s dad said that they shot the 300 BO many times the other day. I guess the new barrel was properly done. I sure hope the barrel people didn’t do another one wrong, and got somebody hurt bad.