What happens when you shoot 300 BLK in your 5.56 AR ?

[GunnyUSMC]

Have you ever wondered? I saw the end results a week or so when I stopped in at Aklys Defense.
I bought my son, Austin, there to meet Joe Meaux and his crew. While we were shooting the bull with Dennis, the Office Manager, I spotted this.



I asked Dennis about it and he said, “That’s what when you shoot 300 Black Out in your 5.56”.
He said a customer brought the damaged rifle in and wanted to know if they could fix it. The lower was fine so they built him a new upper. The customer didn’t want the damaged upper when he picked up his rifle. One of the crew thought it would be cool to mount it in a frame.
You can see the bullet in the cutaway section of the barrel.
I thought it was pretty cool looking. I almost want to blow up an AR just to frame it, but I will refrain.

 

[edwardware]

I've seen similar displays, but never an upper blown entirely in half. The user is fortunate to still have two eyes and ten fingers.

 

[shootstraight57]

It's awful funny about seeing this post.
Yesterday I was packing up my ammo cabinet for a move to the new house when I noticed a few loose .556 rds. ( I keep my mag full all the time). I picked up the loose rounds and proceeded to put them in a half full mag. When I got to the next to the last round I noticed a .300 BLK in my hand and wondered if I had put anymore in that mag. Needless to say I emptied the mag completely and checked and then sat there pondering what would have happened if I ad fired a 300 BLK in my .556. Now you have answered that question.
Thanks Gunny..
I mark all my mags with a p touch sticker so as not to mix them up but evidently I must have had a few rounds in my pocket one day and just threw them in the cabinet.
Nice educational display though..

 

[Art Eatman]

My local gunsmith had that problem brought to him just last week. Only the bolt showed damage, though.

 

[bannockburn]

Gunny

Wow, that's mighty scary looking; glad to hear the owner didn't suffer any injuries from this serious mishap.

I thought it was pretty cool looking. I almost want to blow up an AR just to frame it, but I will refrain.

Thank you for practicing some common sense restraint!

 

[LoonWulf]

Wow, gotta add that to my list of not to dos.
I'd always kinda wondered if a 300 would chamber and fire in a 556, guess I know now.

 

[Odd Job]

Looks like something best avoided!

 

[GunnyUSMC]

It’s another good reason I don’t have a 300 BLK. I built a .277 Wolverine, and the ammo will not chamber in a 5.56.

 

[Delawarean]

What weight .300 bullet was it?

I'd like to calculate its new sectional density!

 

[sota]

if there's anyone that could deliberately blow up an AR like that and do it safely, I'd be willing to bet Gunny could do it

also I was looking at the picture of the opened barrel and was like "there's no way that's just the bullet... it's too long. did it take the case with it too?" then I found this picture...



Holy smokes that 220gr pill is MASSIVE compared to a normal 5.56 round!

 

[H&Hhunter]

I wouldn’t have thought a .300 Blk would chamber in a 5.56...How can it?

 

[Delawarean]

I wouldn’t have thought a .300 Blk would chamber in a 5.56...How can it?

Forward assist, maybe.

 

[H&Hhunter]

Forward assist, maybe.

A good solid forward assist at that! I’m guessing they had to shove the bullet back into the case to get the bolt closed.

 

[LoonWulf]

bolt slamming closed could be enough to push the bullet back into the case i guess, especially if it was pretty close to chambering anyway?

I dunno honestly, while id considered the possibility of one getting into my 556 ar when i had both uppers, i sold the 556 before i had chance to see if a dummy would chamber from a magazine.

 

[sota]

the issue is, it does fit because of the various rounds geometries.
you can see it's very easy for the mistake to go unnoticed.

 

[H&Hhunter]

View attachment 788535
View attachment 788536

the issue is, it does fit because of the various rounds geometries.
you can see it's very easy for the mistake to go unnoticed.

Crazy! Thanks for that photograph and explanation.

 

[GunnyUSMC]

if there's anyone that could deliberately blow up an AR like that and do it safely, I'd be willing to bet Gunny could do it

also I was looking at the picture of the opened barrel and was like "there's no way that's just the bullet... it's too long. did it take the case with it too?" then I found this picture...

View attachment 788530

Holy $)#$ that 220gr pill is MASSIVE compared to a normal 5.56 round!

It’s a very long 22 cal. Bullet now.
Look at the cartridge case in front of the bolt. You can see that the head of the case is missing. Looks like all the pressure was vented into the BCG.

 

[Rembrandt]

That's why I used engraved ejection port covers on oddball calibers.

 

[GunnyUSMC]

That's why I used engraved ejection port covers on oddball calibers.

View attachment 788560

Look at the upper just above the ejection port. It has 5.56 NATO clearly marked on it.

 

[sota]

you could paint the bullets a neon iridescent color and people would still screw it up.

 

[Rembrandt]

Look at the upper just above the ejection port. It has 5.56 NATO clearly marked on it.

Just saying what works for me, for others literacy is an issue....considering what is taught in the public schools, I'm sure this guy at least had good "self esteem".

 

[GunnyUSMC]

Just saying what works for me, for others literacy is an issue....considering what is taught in the public schools, I'm sure this guy at least had good "self esteem".

He might of just had a brain fart.
The dust cover on my .277 Wolverine and 9mm have the caliber marked on them.

 

[Hokie_PhD]

Wow Gunny that’s cool and frightening.

 

[berettaprofessor]

Gunny not only has a cool shop, he sees cool things whereever he goes.

 

[HankC]

Marks upper and use dedicated mag for 300BLK helps but cannot prevent a brain fart moment and that is all needed! Just like reloading, be aware of the risk, check and double check. I have polymer mags for my 300BLK and I don't shoot 223 and 300BLK in the same range trip. Maybe I should have pink handguard for my 300BLK!