AGAIN: 300BLK In 5.56 Rifle -The Firearm Blog

I have successfully avoided the 300BLK evolution that has occurred over the last few years. Mind you, not for any particular reason (other than the cost of stock piling yet another round). For me, suppressing a .38/.357 bolt action Ruger scratches the grin-inducing itch that comes with lobbing lead quietly.

But while the popularity of 300BLK grows, so does the chances of loading one of the oversized rounds into a 5.56mm platform. AR15 member ‘sdman11890’ recounted a hair raising experience from a recent trip to the range involving 300BLK in a friends new 5.56 AR15. He writes:

From the orginal post on AR15.com:

Took a friend of mine out with a rifle I had put together for him a few years ago; he’d never fired it. It’s a Spike’s lower with a PSA complete upper. 16″ Carbine length barrel.

He put about 100 rounds through it without any problems, it was running great.

He loaded up a mag and went to shoot it, and on the second or third round it blew up. It wasn’t too spectacular, smoke out the ejection port, magazine blew out. He was fine.

The BCG was locked up, with the bolt jammed in the extension and the carrier slightly back. I popped the takedown and pivot pins and pulled the upper forward enough to remove it from the lower. We couldn’t get the BCG removed at the range, and broke the charging handle trying to beat it open.

At the time, I thought maybe he had a squib and didn’t notice, or had a double charged load. He had an assortment of ammo, some PMC Bronze 55gr, some Armscor 55gr, some PMC Xtac 62gr, and some Herter’s steel case. The remainder of the mag that hit the ground was loaded with PMC Bronze 55gr.

At the time, I did not even consider that it could be a 300 blackout round. None of us there even own a 300 blackout, and we definitely did not have any ammo around.

Mistakes happen. However the most troubling part of this story is that neither ‘sdman11890’ or his friend own a rifle chambered in 300BLK, leading many to suspect that a 300 round could have ended up in a 5.56 somewhere between manufacturing and sales. In any case, this is a great reminder to remain vigilant when loading magazines.

“Life is like a box of ammo. You never know what you are going to get.”