Just a reminder to pay attention

[shooterrex]

A customer brought this in to the gun shop I used to work at. 300BO doesn't work in a 5.56.  Mark those mags and pay attention. That was a Troy Industries upper.

[unforgiven]

All it takes is a moment of inattention hope no one was hurt 🤕

[BrianK]

It's like many cartridge/shell incompatibilities, don't have them anywhere near each other. I'm sure there are alot that I don't know about but the classic for me was 20ga and 12ga. since I used both, just not on the same day. Shoot one or the other and make sure the vest was totally stripped of shells after the hunt was over. Double check it before going out again. 

[shooterrex]

No one was hurt. Just had to change his shorts.

[E5232]

That's a bad day for sure.  I watched a Mini 14 suffer the same fate, when my cousin whose a bit dull do begin with, somehow chambered a .30 carbine round, and kaboom. Not sure how you mix those two but at the days end, a .30 bullet, and a .22 cal barrel do not good friends make on any platform.

[Madhouse]

Man people really need to pay attention...

[98Z5V]

21 hours ago, shooterrex said:

300BO doesn't work in a 5.56. 

How did it even chamber?  How did the bolt rotate? 

[98Z5V]

If the bolt doesn't fully rotate, the firing pin will never be able to touch the primer.  No way.

There's more to this story.

[Sisco]

8 minutes ago, 98Z5V said:

How did it even chamber?  How did the bolt rotate? 

Was wondering that.  But 300 blk brass are shorter so maybe it can close the bolt. Was it maybe a 5.56 round in a 300Blk? That would not be good either. 

[Sisco]

7 minutes ago, Sisco said:

Was wondering that.  But 300 blk brass are shorter so maybe it can close the bolt. Was it maybe a 5.56 round in a 300Blk? That would not be good either. 

Or maybe he doesn’t want to admit he double charged a handload with pistol powder by accident?

Another thought: If the 300 Blk wasn’t crimped, it could drive the bullet back into the brass, possibly enough to let the bolt close and increasing pressures dramatically.

Edited September 18, 2022 by Sisco

[98Z5V]

The BLK cartridge (diameter at neck) will keep the BCG from going forward.  Enough that the cam pin won't even reach the cutout in the upper.  The bolt can't rotate, unless that cam pin is IN the cutout - hence, the entire reason for it, and all it does, really. 

Like I said, there's more to this story.

[Sisco]

13 minutes ago, 98Z5V said:

The BLK cartridge (diameter at neck) will keep the BCG from going forward.  Enough that the cam pin won't even reach the cutout in the upper.  The bolt can't rotate, unless that cam pin is IN the cutout - hence, the entire reason for it, and all it does, really. 

Like I said, there's more to this story.

Okay, I was thinking that the 300 Blk is quite a bit shorter then a 5.56 brass, and if the bullet wasn’t crimped it might push the bullet far enough into the brass that the cam pin might be able to barely reach the cut out, especially if the Blk brass had been sloppily made from 5.56 and cut too short. Can’t say without having some right in front of me to look at and they are in the garage right now. Well like you said whatever, there is more to the story.

[Sisco]

Answer:

https://www.windhamweaponry.com/beware-that-300-blackout-ammo-can-be-chambered-in-a-5-56-223-chamber-with-catastrophic-results/

[98Z5V]

I guess that answers that.  I only load 150gr Hornady FMJ-BTs for 300 BLK range ammo.  Most people don't load the light stuff, but I don't think it would make a difference.

Here's how far a BCG will close on a 5.56 barrel, with the 150s loaded - nowhere near cam pin rotation:

 

[Sisco]

Must be dependent on specific bullet types then is the only thing I can figure.

[98Z5V]

We may never know, AL - but I'll keep researching this.  I'll start measurements of BCG travel where cam pin rotation starts, and figure it out from there. 

EDIT - I have no doubt in my mind that the stuff you posted from WW is exactly right.  Now, I want to see why. 

Edited September 18, 2022 by 98Z5V

[shooterrex]

I didn't save the pics of the 30 cal bullet stuck in the throat of the barrel. It was stuck in there.

[98Z5V]

13 minutes ago, shooterrex said:

I didn't save the pics of the 30 cal bullet stuck in the throat of the barrel. It was stuck in there.

Any idea what ammo that dude was trying to shoot?  I mean, what BLK ammo, through his 5.56 gun?... 

[JMJ]

47 minutes ago, 98Z5V said:

Any idea what ammo that dude was trying to shoot?  I mean, what BLK ammo, through his 5.56 gun?... 

I’d really like to know that as well just for peace of mind since I have both cartridges. I’d read about the issue in the past, iirc it was mainly just an issue with the different 110gr bullets since their ogive is slimmer it can add to “tolerance stacking” along with bullet setback from the bolt slamming home and in one instance the shooter forced the bolt home with the fwd assist. 

[dpete]

Short little 110 grain bullets like a varmageddon in a non crimped case COULD set back far enough into the case to allow the bolt to close and lock up. That is why I never load 223 and 300 BLK at the same time. 223 goes in FDE mags and BLK goes in black to further prevent confusion.

[JMJ]

38 minutes ago, dpete said:

Short little 110 grain bullets like a varmageddon in a non crimped case COULD set back far enough into the case to allow the bolt to close and lock up. That is why I never load 223 and 300 BLK at the same time. 223 goes in FDE mags and BLK goes in black to further prevent confusion.

I’ve been taking a similar approach, in only using fde 30rd mags or metal 20rd mags with 300blk and all black pmags (20’s/30’s) with 5.56/223. I do keep both my 300blk and 5.56 pistol uppers and the lower in a case together, but I pickup all ammo and designated mags for the upper not in use before I take out mags for the one I’ll be using. I had seen these sorta warnings before I built my blackout so I’ve tried to stay mindful, especially since I only shoot 110gr and 120-125gr supers through mine. 

[shooterrex]

I sent the guy that sent me the pics a message. Maybe he can find out what ammo it was.

[shooterrex]

[dpete]

Just for comparison:                Picture robbed from my 375 Socom thread.

Left to right.

5.56               6.5 Grendel                      300 BLK             375 Socom

Thats a 55 gr 223 and a 110 gr Varmageddon in the BLK.  Granted it isn't a side by side comparison, but you can see the ogive of the BLK isn't to far forward of that same diameter on the 223 case.  A good slam forward on a non-crimped case can get you in trouble.

[BrianK]

I'd be willing to bet that the 85s that I load would easily go into the chamber of a .223. No, I'm not going to try it.

That's why I never, and I do mean never, have any gear having to do with either cartridge anywhere near the other. If someone will screw up, well, let me rephrase, I can get confused and I don't want to "be that guy" !