Just in case you were wondering???

[bionic knees]

how do you get a 300 blk far enough into a .223 chamber to fire???

 

[GWS]

how do you get a 300 blk far enough into a .223 chamber to fire???

Just let the bolt close.
The .300 BLK fits quite nicely in a 5,56 chamber

 

[Caveman Jim]

When I did my first build, 300BLK, I made the distinction of using 20 round Pmags and bought the 300BLK bands for the magazines. I do not use the 20 rounders in anything but 300BLK pistol.

For the 223 I use USGI 30's exclusively for my kit, GHB, BOB and my backpack with the 7.5" pistol build.
I do use 5.56 bands on a few 30 round Pmags for range shooting.

I am confident with this arrangement

 

[arakboss]

how do you get a 300 blk far enough into a .223 chamber to fire???

Super sonic round was my guess?

 

[gmerkt]

I didn't have a scratch. Barrel, upper & lower receivers and BCG were all toast. Magazine blew apart but was reusable. Some rounds in the mag were gorked up. Found some sharp chunks of aluminum here n there. After 30 mins looking around, I happily found my new T1 optic under a bench about 10-15 yds away.

Mention of a bench suggests this might've happened on a range. When one of those guns blows up, the broken pieces become the equivalent of shrapnel and you have to hope that no other shooters get injured. Unless the bench is walled in. Which I don't often see on rifle ranges, as you sometimes see on the pistol end. One of the ranges where I'm a member has portable screens that you can erect on the side of the bench, the purpose of which is to keep ejecting brass from hitting a neighbor. They probably wouldn't be of much use in protecting against broken rifle parts flying through the air under force.

I marvel at the number of times I've heard of blown up AR's, yet shooters usually don't get seriously injured. My pal in NM loaded some cartridges with 20-something grains of 800X instead of H322. Violating the rule of having only one bottle of powder on the bench at one time. His rifle blew big time, yet he only got slightly peppered in the face. It may be that the aluminum material in the upper tends to blow out to the sides, maybe.

 

[Alexx1401]

Add me to the glad you came out of it intact. Closest I have done so far is a 10mm out of a .45 ACP . Have a PCC that uses both, just swap parts. I swapped at the range one day and its kind of dark in the damn lane. Put the new bolt group and barrel, forgot the mag I had was still 10mm. Shot of course had "strange sound and did not cycle. As soon as I pulled the bolt back and saw the blown 10mm case I knew what I had done. The slug did make it out the barrel and down range. Told me next time be more careful showing off how the little rifle can shoot both calibers

 

[TTSX]

I just don't own a .300blk problem solved.

 

[Roadkill Bill]

how do you get a 300 blk far enough into a .223 chamber to fire???

My guess is that the bullet, pushed back slightly, into the case, as the bolt was released.
im guessing the bullet never made it down the barrel. I tried to remove the barrel from the receiver but it acts like the barrel lug is welded on. I'm also guessing that as the round detonated, the barrel swelled to the point the barrel lug is no longer removable.
I'm torn between keeping the upper as is, as a de facto work of art, or demolishing it so I can get a peek at what happened inside the chamber, and to see if the bullet actually made any entry into the barrel.
I can't even remove the rear, Magpul sight, because of the swelling to the receiver.

 

[Roadkill Bill]

I just don't own a .300blk problem solved.

I really like the round and was intrigued with having the versatility of being able to shoot both calibers, using the same receiver. I had even painted the magazine floor plates, so I could distinguish the two rounds from each other. I didn't accidentally use the wrong round, I actually thought I had a .300 upper on the weapon.
in retrospect though, I concede that you are the wiser man.

 

[Flopsweat]

My guess is that the bullet, pushed back slightly, into the case, as the bolt was released.
im guessing the bullet never made it down the barrel. I tried to remove the barrel from the receiver but it acts like the barrel lug is welded on. I'm also guessing that as the round detonated, the barrel swelled to the point the barrel lug is no longer removable.
I'm torn between keeping the upper as is, as a de facto work of art, or demolishing it so I can get a peek at what happened inside the chamber, and to see if the bullet actually made any entry into the barrel.
I can't even remove the rear, Magpul sight, because of the swelling to the receiver.

I've tried chambering a few different commercial 300BLK cartridges in a 5.56 just to see, not to shoot. All of them went into battery and most or maybe all compressed just as you said. I wouldn't expect a .3" slug to go down a .22" barrel very far if at all.

 

[Ben B.]

But 300 BLK with a silencer and subs is so much giggity-goo fun to plink with.

 

[ma96782]

RE : Post #27

That confirms it.

I want to sell off or trade my .300 blackout.

Aloha, Mark

 

[bionic knees]

Just let the bolt close.
The .300 BLK fits quite nicely in a 5,56 chamber

can't quite get my head around that, although I have never seen a .300 blk round in person.

 

[Caveman Jim]

can't quite get my head around that, although I have never seen a .300 blk round in person.

5.56 vs 300 Blackout | The Ultimate AR Caliber Showdown!

We dive into 5.56 vs 300 blackout round in an indepth article covering terminal ballistics, the history 5.56 and 300 blackout, and more!

lynxdefense.com

 

[bionic knees]

5.56 vs 300 Blackout | The Ultimate AR Caliber Showdown!

We dive into 5.56 vs 300 blackout round in an indepth article covering terminal ballistics, the history 5.56 and 300 blackout, and more!

lynxdefense.com

View attachment 1171238

thank you, the comparison makes much better.

 

[Caveman Jim]

thank you, the comparison makes much better.

You're welcome, the 300 blackout round in the picture is probably a subsonic bullet which are 180 to 220 grains that are a lot fatter than this 125 grain hollowpoint super sonic round that I shoot. And seeing a different angle of the two might make it a little easier to see how they would intertwine in the same chamber.

 

[jbett98]

John Wayne figured this problem out.

 

[bionic knees]

You're welcome, the 300 blackout round in the picture is probably a subsonic bullet which are 180 to 220 grains that are a lot fatter than this 125 grain hollowpoint super sonic round that I shoot. And seeing a different angle of the two might make it a little easier to see how they would intertwine in the same chamber.

View attachment 1171276

yup, absolutely, I was picturing shoving a .308 win into the .223 chamber .300 blk and .308 win are much different cartridges.