Firing a .300 Blackout in a .556 Chamber

date: June 21, 2018

.300 Blackout vs .556

AM-15 KEYMOD, .300BLK 16″ – M4

If you’re like me you, you never take just one weapon to the range. As far as I’m concerned, whether or not range day is a success is directly tied to how many weapons I shoot.  Multiple guns usually means multiple calibers. I hate to admit it but there have been times where I was not paying attention and started to load the wrong ammo in a magazine. I have never gotten as far as trying to fire a pistol or rifle with the wrong ammo, but I’ve been close.

The Two Rounds Are Very Similar

The .300 Blackout was created to to fill the needs of operators who wanted .30 caliber performance but didn’t want to change all their equipment. The .300 Blackout round allows you to just retrofit the barrel on your AR platform and you are ready to shoot. Same magazines and same bolt.

If you’re not paying attention, mixing up .300 blackout and .556 ammo can be easy to do. The rounds are the same length, the cases are generally the same diameter, and they both fit in the same magazines. Maybe you left some magazines loaded from the last range day and forget to check it before you load your rifle. It’s also possible that some loose ammo ended up in the bottom of your range bag and a round or two of .300 blackout ends up in the middle of a magazine full of .556.

No matter how it happens. firing a .300 blackout in a .556 barrel always leads to bad things. It’s easy to find lots of pictures of the results. Now you can go over The Firearm Blog and watch a video of it. They also have a lot of good pictures with the video. Click on the picture to go The Firearm Blog.

.300 Blackout in a .556 Image courtesy of The Firearm Blog