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Posted: 12/4/2020 8:12:38 PM EDT
Pictured below is a .223 and a 300BO in each others case gauge. I didn't force either one they sit just where they stopped. How do you get a KB when the cartridges won't fit in each others chambers? Unless under spring pressure it could force the case into the chamber?
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Posted: 12/4/2020 9:06:51 PM EDT
[#1]
Obviously it has happened several times as their are many photo's of blown up guns.
Get a 300 blk case and set it in the 223 case gauge and report back. There is a photo of a cut away 5.56 chamber with a 300blk in it floating around on the interweb. What happens is the bcg sends the round home, it sets the bullet back into the case (thus further increasing pressure) then when the magic silver button in the base of the case gets hit you are now swaging a .308 caliber bullet down a .224 caliber bore.....pressure has to go somewhere. There is also another cut-away barrel showing a squib 300 blk bullet. it's like 1.5" long! 
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Posted: 12/4/2020 9:26:40 PM EDT
[#2]
Never underestimate the potential of a guy banging on the FA repeatedly.....
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Posted: 12/4/2020 10:17:46 PM EDT
[#3]
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Posted: 12/4/2020 10:19:48 PM EDT
[#4]
In the last two years as a RSO at my range. I have seen three KB this way. It happens a lot
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Posted: 12/4/2020 10:25:35 PM EDT
[#5]
Why are you even doubting it can happen?
The fact it does happens settles that. How it happens is immaterial. |
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Posted: 12/4/2020 11:31:33 PM EDT
[#6]
Quote HistoryQuoted: In the last two years as a RSO at my range. I have seen three KB this way. It happens a lot Probably 1 out of 10 guys who KB a gun actually post about it on the internet. I have seen at least a dozen posts on 300BO in 556 KBs on the internet over the past few years (several different gun forums). You can deduce: it happens quite a bit! |
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Posted: 12/5/2020 12:26:40 AM EDT
[#7]
Quote HistoryQuoted: Probably 1 out of 10 guys who KB a gun actually post about it on the internet. I have seen at least a dozen posts on 300BO in 556 KBs on the internet over the past few years (several different gun forums). You can deduce: it happens quite a bit! Quote HistoryQuoted: Quoted: In the last two years as a RSO at my range. I have seen three KB this way. It happens a lot Probably 1 out of 10 guys who KB a gun actually post about it on the internet. I have seen at least a dozen posts on 300BO in 556 KBs on the internet over the past few years (several different gun forums). You can deduce: it happens quite a bit! This one was three weeks ago at my range. I had to give first aid to the guy. He was holding the magwell and it split cutting his hand.  Attached File |
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Posted: 12/5/2020 12:59:06 AM EDT
[#8]
Lighter shorter bullets allow 300 BO to chamber fine in a 223.
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Posted: 12/5/2020 1:05:12 AM EDT
[#9]
There's a reason it's known as 300 Blowup!
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Posted: 12/5/2020 1:58:50 AM EDT
[#10]
I have photos somewhere of a gun I had to beat apart to find out what happened. Knocked the elongated bullet out too. I’ll post them if anyone wants to see, not that it’s anything all that uncommon.
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Posted: 12/5/2020 7:41:00 PM EDT
[#11]
I assure you it is entirely possible to insert, and fire a 300BK supersonic round in a .223 / 5.56 chamber.
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Posted: 12/6/2020 8:24:00 AM EDT
[#12]
When the 300 chambers into the smaller chamber the bullet gets set back into the case thus allowing the bolt to lock up.
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Posted: 12/8/2020 1:44:33 AM EDT
[#13]
I’ve never actually bought a factory 300 blackout round. I have tested my 300 handloads to see if they will chamber in my .223 guns. The bolt will not close on them. However, if I were to really TRY to force close the bolt I could push the bullet back into the case a couple thousandths enough for the round to chamber.
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Posted: 12/9/2020 7:28:21 AM EDT
[#14]
This is the reason why if I have both 5.56 and .300 BLK rifles with me at the range I use FDE or grey USGI aluminum mags for 5.56, and black PMAGs or black aluminum mags for the .300 BLK. That way I can tell by the color of the magazine which is which.
I mostly shoot my handloads in the .300, the vast majority of which are subsonic with long heavy bullets. My subsonic loads won’t chamber in a 5.56 unless I really tried to force it by pounding on the forward assist and set the bullet back in the case. Some loads I could see being able to fit a 5.56 chamber, especially the short light supersonic bullets like the 110gr VMax and similar. Just pay attention and be careful. |
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Posted: 12/11/2020 2:42:29 PM EDT
[#15]
Quote HistoryQuoted: This is the reason why if I have both 5.56 and .300 BLK rifles with me at the range I use FDE or grey USGI aluminum mags for 5.56, and black PMAGs or black aluminum mags for the .300 BLK. That way I can tell by the color of the magazine which is which. Just pay attention and be careful. Multiple ways to skin that incompatibility cat. Alternative way of looking at the safe segregation issue: I intentionally do NOT try to segregate 300 from 5.56 by the type of magazine it's loaded into. Relying on magazine identification works great up until it doesn't. By forcing myself to take the few extra seconds to look at the cartridges themselves (rather than grabbing the "correct" magazine), I remove a possible failure point. |
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Posted: 12/11/2020 2:56:15 PM EDT
[#16]
I have green painters tape and blue painters tape. All 300 Blk guns and mags get green painters tape around the gun and mags, all 5.45x39 guns get blue painters tape around the gun and around the mags.
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Posted: 12/13/2020 1:56:09 AM EDT
[#17]
Pmags for 556/223, translucent Lancer mags for 300 BLK for me. Also my 223 rifles all have quad rails, while my blackout rifles are MLOK.
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Posted: 12/13/2020 2:40:16 AM EDT
[#18]
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Posted: 12/13/2020 9:31:57 AM EDT
[#19]
my daughter's fav rifle is a .300blk w/ a 16" barrel (great pig gun)- it's black. My preferred HD gun is a .300blk w/ a 10.5- in FDE.
We also have 5.56 rifles in the same configurations but opposite colors. We have a hard and fast rule at the range-- only one caliber rifle/ammo out of the cases at one time. It would be VERY easy to get things mixed up.... I need to thin the herd a bit... |
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Posted: 12/13/2020 10:04:24 AM EDT
[#20]
I am using a different mag(kinda, teflon Surefeed) for my 300BO guns. I also have Yellow(what I had) electrical tape wrapped around at the bottom of those mags as well as around the buffer tube right behind the castle nut. That way if the gun has yellow tape it needs a mag with yellow tape. Also my 300BO's have MLOCK & Keymod HG's where none of my other guns do. Even with all that I still only have one gun out at a time when shooting.
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Posted: 12/13/2020 4:53:29 PM EDT
[#21]
I have the same concern with my .308 and .358 Win. I have not heard that it has happened or can happen, but I work with the premise that it's possible. As with 5.56/.300BO, I can easily spot the difference between .308/.358 Win., but mistakes can happen. My volume of .358 downrange is a small fraction of those of a typical .300BO shooter so I can spend the time and energy to mark that cartridge in addition to the normal steps ( mag ID, upper ID, physical separation etc.). I have tried coating the brass with red high temp anodized coating but had fouling like the old varnished steel ammo of the past. It also wouldn't hold up to case cleaning/prep and fouled sizing dies. I also tried Brass Black which works pretty good, but it looks like you're using old range pick-up ammo that you found in the dirt. My solution ended up by simply marking a red band on the case of the .358's below the shoulder. Milwaukee Inkzall works twice as good as a Sharpie. It's not a 100% solution but just another measure that may help.
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Posted: 12/13/2020 4:59:18 PM EDT
[#22]
Quote HistoryQuoted: I have the same concern with my .308 and .358 Win. I have not heard that it has happened or can happen, but I work with the premise that it's possible. As with 5.56/.300BO, I can easily spot the difference between .308/.358 Win., but mistakes can happen. My volume of .358 downrange is a small fraction of those of a typical .300BO shooter so I can spend the time and energy to mark that cartridge in addition to the normal steps ( mag ID, upper ID, physical separation etc.). I have tried coating the brass with red high temp anodized coating but had fouling like the old varnished steel ammo of the past. It also wouldn't hold up to case cleaning/prep and fouled sizing dies. I also tried Brass Black which works pretty good, but it looks like you're using old range pick-up ammo that you found in the dirt. My solution ended up by simply marking a red band on the case on the .358's below the shoulder. Milwaukee Inkzall works twice as good as a Sharpie. It's not a 100% solution but just another measure that may help. 6.5 creed will also fit in a 308 |
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Posted: 12/13/2020 5:13:16 PM EDT
[#23]
Quote HistoryQuoted: 6.5 creed will also fit in a 308 Quote HistoryQuoted: Quoted: I have the same concern with my .308 and .358 Win. I have not heard that it has happened or can happen, but I work with the premise that it's possible. As with 5.56/.300BO, I can easily spot the difference between .308/.358 Win., but mistakes can happen. My volume of .358 downrange is a small fraction of those of a typical .300BO shooter so I can spend the time and energy to mark that cartridge in addition to the normal steps ( mag ID, upper ID, physical separation etc.). I have tried coating the brass with red high temp anodized coating but had fouling like the old varnished steel ammo of the past. It also wouldn't hold up to case cleaning/prep and fouled sizing dies. I also tried Brass Black which works pretty good, but it looks like you're using old range pick-up ammo that you found in the dirt. My solution ended up by simply marking a red band on the case on the .358's below the shoulder. Milwaukee Inkzall works twice as good as a Sharpie. It's not a 100% solution but just another measure that may help. 6.5 creed will also fit in a 308 Yes but a smaller bullet won’t result in a KB. |
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Posted: 12/13/2020 5:43:53 PM EDT
[#24]
Quote HistoryQuoted: 6.5 creed will also fit in a 308 Although it certainly won't do your chamber or rifling any favors, I'm not sure you would get a KB if fired. If it didn't fireform it would split the neck and the bullet would bounce off the walls. I wouldn't want to try it. Same with a .308 fired in a .358 chamber, which also fits. Now a 6.5 Creedmoor in a .358 Win could get interesting. I'm not a wildcatter so I don't how much is safe to fireform. I wonder if a .308 could possibly chamber in a 6.5? |
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Posted: 12/13/2020 8:21:21 PM EDT
[#25]
Quote HistoryQuoted: I have the same concern with my .308 and .358 Win. I have not heard that it has happened or can happen, but I work with the premise that it's possible. As with 5.56/.300BO, I can easily spot the difference between .308/.358 Win., but mistakes can happen. My volume of .358 downrange is a small fraction of those of a typical .300BO shooter so I can spend the time and energy to mark that cartridge in addition to the normal steps ( mag ID, upper ID, physical separation etc.). I have tried coating the brass with red high temp anodized coating but had fouling like the old varnished steel ammo of the past. It also wouldn't hold up to case cleaning/prep and fouled sizing dies. I also tried Brass Black which works pretty good, but it looks like you're using old range pick-up ammo that you found in the dirt. My solution ended up by simply marking a red band on the case of the .358's below the shoulder. Milwaukee Inkzall works twice as good as a Sharpie. It's not a 100% solution but just another measure that may help. You have no worry for 358 win. It physically won't fit as the case is the same length as it's parent case. Where you run into problems is where the case is short enough to fit into the chamber that has an oversized bullet. For example say you had a .243 win, it's possible that a 30BR could chamber and fire in the 243 having the same issues like the 300blk. |
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Posted: 12/13/2020 11:22:56 PM EDT
[#26]
Quote HistoryQuoted: You have no worry for 358 win. It physically won't fit as the case is the same length as it's parent case. Where you run into problems is where the case is short enough to fit into the chamber that has an oversized bullet. For example say you had a .243 win, it's possible that a 30BR could chamber and fire in the 243 having the same issues like the 300blk. Well now you tell me! Seriously, thank you. I did at one time attempt to manually cycle a dummy .358 cartridge through my LR 308. It did result in some bullet set-back, bullet marking, and brass damage, and although I couldn't picture the cartridge going into battery and firing, I decided to play it safe. Thanks again for the reassurance. |
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Posted: 12/15/2020 11:11:16 AM EDT
[#27]
I have mag bands on both the upper and the mag for both my 5.56 and .300blk uppers. It CAN happen, but it isn't much of a concern for me. Every mag that is loaded is marked, even the ones that sit in the safe.
To start....I don't shoot much 5.56....I prefer to shoot the cheaper (and far more fun) .22LR. More importantly , I hardly ever shoot brass (brass colored case) supersonic FMJ in .300blk. I've shot a little bit of S&B supersonic, but that is about it. My S&B is usually subsonic...which is a bit harder to chamber and easy to spot with their powder blue primers. If you are paying so little attention that you manage to mix up a 200gr FMJ .300blk round with a 55gr FMJ 5.56 round, you should probably not handle weapons anyway. I have Australian Outback FMJ, which has a black case. I have Wolf Steel FMJ which obviously has a gray case. I also have a little bit of Tac-Tx, which has a black tip, and a shot more V-max than anything else, which has a red tip. Most of my 5.56 that are still in boxes are 75gr/77gr OTM's anyway. It would be hard to mix up. |
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