I blew up my rifle!

[Old Man with Gun]

Any chance the case was too long and caused an excessive construction around the bullet when chambered? Those are soft bullets.
If you didn't have an over charge, wrong powder, or barrel obstruction this is my only guess. The bullet being pushed into the case could increase pressure, but I doubt that much.

 

[Tokay444]

With the amount of brass beyond the neck of the chamber it’s quite likely.

 

[BuildingConceptsllc]

Any chance the case was too long and caused an excessive construction around the bullet when chambered? Those are soft bullets.
If you didn't have an over charge, wrong powder, or barrel obstruction this is my only guess. The bullet being pushed into the case could increase pressure, but I doubt that much.

That's what I guessed ITT a while back on page 2, but never saw any answer to it. It looked long to me but hard to tell of course from a pic. That's the only thing I could think of that would do it other than a barrel obstruction. Without pistol powder , I don't think you can get enough in the case to do that by itself.

 

[Southernspeed]

Any chance the case was too long and caused an excessive construction around the bullet when chambered? Those are soft bullets.
If you didn't have an over charge, wrong powder, or barrel obstruction this is my only guess. The bullet being pushed into the case could increase pressure, but I doubt that much.

I've used that and the other cases before, all the others are right at min trim length, I've no reason to believe the blown one was any different.

 

[Tokay444]

I've used that and the other cases before, all the others are right at min trim length, I've no reason to believe the blown one was any different.

Was it trimmed before being loaded?

 

[Southernspeed]

That's what I guessed ITT a while back on page 2, but never saw any answer to it. It looked long to me but hard to tell of course from a pic. That's the only thing I could think of that would do it other than a barrel obstruction. Without pistol powder , I don't think you can get enough in the case to do that by itself.

It certainly would explain a lot but it's the same length and thickness neck as the rest.

 

[Southernspeed]

Was it trimmed before being loaded?

They were all checked/ (if needed)trimmed before last loading.

 

[Southernspeed]

Any chance the case was too long and caused an excessive construction around the bullet when chambered? Those are soft bullets.
If you didn't have an over charge, wrong powder, or barrel obstruction this is my only guess. The bullet being pushed into the case could increase pressure, but I doubt that much.

I'm still leaning towards double charge but even then, would it really cause that much damage? I may have to buy quick load just to settle my mind!!

 

[Old Man with Gun]

I'm still leaning towards double charge but even then, would it really cause that much damage? I may have to buy quick load just to settle my mind!!

A double charge does not double the pressure it is far, far worse.

 

[Southernspeed]

A double charge does not double the pressure it is far, far worse.

Even more reason to find out what pressure it would create. If I knew for sure that a double charge would absolutely cause this damage, at least I'd 'know' why it happened, call myself a dumbass and move on. I was testing loads in a bolt gun today, felt a little apprehensive but ok, but the thought of rebuilding and shooting that same AR without knowing why it happened does not fill me with joy!

 

[Plinker 73]

I saw exactly the same kind of damage when a friend of mine shot a shit load of .22 rimfire through his M-16 with an adaptor. Then fired a 5.56 without cleaning the lead from the bore. The damage was as extensive as the pictures show. Only difference his lower wasn’t damaged. Pure luck. Looks like a bore obstruction to me.
Just my .02 worth.

 

[Southernspeed]

I saw exactly the same kind of damage when a friend of mine shot a shit load of .22 rimfire through his M-16 with an adaptor. Then fired a 5.56 without cleaning the lead from the bore. The damage was as extensive as the pictures show. Only difference his lower wasn’t damaged. Pure luck. Looks like a bore obstruction to me.
Just my .02 worth.

Definitely not a bore obstruction. I know it was clear plus the bullet hit the target.

 

[Old Man with Gun]

If there was a bore obstruction there is likely a barrel bulge now. Get a jag and tight patch and you will feel the spot as easier to push through if it is there.

 

[Southernspeed]

If there was a bore obstruction there is likely a barrel bulge now. Get a jag and tight patch and you will feel the spot as easier to push through if it is there.

No bulge, discolouration etc

 

[ironman56]

Definitely not a bore obstruction. I know it was clear plus the bullet hit the target.

If the bullet hit the target , there's only one thing it could be , GREMBLINS, did you feed the blackout after midnight?

 

[ironman56]

All joking aside, this kinda worries me as I reload alot, and now every time I go to the range it's gonna be in the back of my mind , so hopefully it will up my reloading game. Thanks for posting the info even if we don't know the exact cause yet.

 

[Southernspeed]

All joking aside, this kinda worries me as I reload alot, and now every time I go to the range it's gonna be in the back of my mind , so hopefully it will up my reloading game. Thanks for posting the info even if we don't know the exact cause yet.

If I could find out what pressure a double load produces, that would help a lot.

 

[Twitchy]

What's the twist rate of the barrel?

Also, I know you mentioned it was the first shot, but were you shooting Berry's before this round?

I ask these questions because, Berry's has a max twist rate rating of 1:7 and a velocity below X.

These rounds will start coming apart with a faster twist rate or too high of a velocity. Heck, sometimes they come apart just because.

I got crazy erratic down range results with mine. I also had a ton of debris in the suppressor, barrel, chamber, and lower receiver. I can see a chunk of something causing an obstruction. Once I realized this issue, I cleaned chucks of the bullets out of everything.

 

[Southernspeed]

What's the twist rate of the barrel?

Also, I know you mentioned it was the first shot, but were you shooting Berry's before this round?

I ask these questions because, Berry's has a max twist rate rating of 1:7 and a velocity below X.

These rounds will start coming apart with a faster twist rate or too high of a velocity. Heck, sometimes they come apart just because.

I got crazy erratic down range results with mine. I also had a ton of debris in the suppressor, barrel, chamber, and lower receiver. I can see a chunk of something causing an obstruction. Once I realized this issue, I cleaned chucks of the bullets out of everything.

It’s 1:7 and I was aiming for right around 1000fps. The bullet reached the target (50yds) and left a good round hole. I have tried Berry’s before but not many.

 

[Cynical]

I'm just throwing this out there after seeing the remains of your brass. These pics are of once fired/processed LC 308 cases from TOP BRASS, bought way back in the early 20teens. These have been reloaded/fired one time. The failures are in the absolute strongest part of the brass, and are failures of the brass itself, not case head separation. One of the rounds blew the Pmag out of the gun and rendered the mag useless due to the mag catch groove being stripped out of the plastic body. I think these could have easily been more catastrophic.
After realizing the brass was at fault, I used a light to inspect the interior of the remaining cases I hadn't yet loaded. I found approximately 45-50 more cases (out of about 800 cases) with the interior cracks around the flash hole. (These were still in a sealed bag, unused) I finally forced myself to go ahead and cull every LC case I had from that lot. I still have probably 1200 or so rounds of this brass that I had already loaded that I have yet to pull the bullets and salvage the components. The headstamps spanned several years, so I can't say it's isolated to 1 lot from the factory. I don't see how Top Brass could have damaged it in this way in the processing. Could it be possible you got ahold of some brass with the same damage/defect? Just another remote possibility to consider.

ETA: I did find similar case failure on some other forums, but in each case it was LC 308. No other caliber

These are Lapua 6br with similar failures in a very strong part of the case. No obstructions, not overcharged. Not trying to derail the thread just wanted to provide a similar example of a weird failure.

 

[Makinchips208]

If I could find out what pressure a double load produces, that would help a lot.

I have reloaded and burned more than a few pounds of h110 in 44mag loads. And some respected people I knew all told me the same thing, “don’t reduce loads with h110.”
How that relates to your situation? I don’t know, just maybe there is something to the ‘wisdom’ of never loading ammo with cases that are far from full when using h110?
As a note regarding pressure, Hodgdon lists

19.4gr H110, a 110gr bullet, at 48,400psi
Obviously that much powder behind a 220 gr would exceed the strength of the rifle.

Maybe you have access already but here is a couple published loads, similar to what you had, although different brass and bullet obviously can cause variations.

Here is a screenshot of Hodgdon data.

And here is a screenshot of Sierra data.

 

[Southernspeed]

I have reloaded and burned more than a few pounds of h110 in 44mag loads. And some respected people I knew all told me the same thing, “don’t reduce loads with h110.”
How that relates to your situation? I don’t know, just maybe there is something to the ‘wisdom’ of never loading ammo with cases that are far from full when using h110?
Maybe you have access already but here is a couple published loads, similar to what you had, although different brass and bullet obviously can cause variations.


Here is a screenshot of Hodgdon data.
View attachment 8286382

And here is a screenshot of Sierra data.
View attachment 8286384

I did some testing a while back with 150gr bullets at subsonic. I think that was with h110. Wildly variable velocities as the powder uncovered the primer. If you pointed the rifle up, tapped it then gently lowered it to firing position you could get consistent speed. Not even sure if a case filler would work in those circumstances.

 

[Makinchips208]

interesting. Did they go slower if you left the primer uncovered? Or faster?

 

[Old Man with Gun]

What's the twist rate of the barrel?

Also, I know you mentioned it was the first shot, but were you shooting Berry's before this round?

I ask these questions because, Berry's has a max twist rate rating of 1:7 and a velocity below X.

These rounds will start coming apart with a faster twist rate or too high of a velocity. Heck, sometimes they come apart just because.

I got crazy erratic down range results with mine. I also had a ton of debris in the suppressor, barrel, chamber, and lower receiver. I can see a chunk of something causing an obstruction. Once I realized this issue, I cleaned chucks of the bullets out of everything.

Be careful how you load the Berry 220. If you don't chamfer and flare the neck some you can end up shaving off part of the thin jacket on the case mouth. Only use enough crimp to make the neck flush. I have loaded and shot thousands of these with no issue - velocity 1050ish. BUT before I figured out the chamfer, flair, min crimp I had some eratic results.

 

[B y r o n]

What's the twist rate of the barrel?

Also, I know you mentioned it was the first shot, but were you shooting Berry's before this round?

I ask these questions because, Berry's has a max twist rate rating of 1:7 and a velocity below X.

These rounds will start coming apart with a faster twist rate or too high of a velocity. Heck, sometimes they come apart just because.

I got crazy erratic down range results with mine. I also had a ton of debris in the suppressor, barrel, chamber, and lower receiver. I can see a chunk of something causing an obstruction. Once I realized this issue, I cleaned chucks of the bullets out of everything.

At least get the information correct:

"Bullet O.A.L.: 1.350"

Cartridge Name: 300 AAC Blackout
Cartridge O.A.L.: 2.150"

1:7" Twist Rate Barrel Max Velocity: 1300 fps

1:5" Twist Rate Barrel Max Velocity: 1000 fps

• Load data for our Superior Plated Bullets® can be found in any manual or on any powder manufacturer’s website.
• Cast or jacketed data with the same grain weight and profile will work with our bullets.
• You can use a taper or a roll crimp.
• Don’t over crimp the brass after seating. This causes bullet core separation, leading to increased copper fouling and accuracy issues.
• Don’t exceed the recommended maximum velocities listed. This creates bullet core separation and accuracy issues."

 

[mtrmn]

These are Lapua 6br with similar failures in a very strong part of the case. No obstructions, not overcharged. Not trying to derail the thread just wanted to provide a similar example of a weird failure.

Do you still have these cases? If so, look inside with a light to see if there are cracks in the case head base around the flash hole. What's the history on these cases? How many firings, were they commercially processed fired cases? How did you re-size them? I really would like to figure out what causes this. These are the first non-LC cases I've witnessed in this condition.

 

[srt-4_uk]

In case you were still wondering, I took a barrel extension off a shot out Noveske barrel and put it in a spare upper I have so I can test the OOB firing. Plus side is no barrel blocking the view.
Warning: long winded post coming.
Cliffs: parts in spec can't cause an OOB discharge.

I put the Noveske extension in the new upper and threw on a barrel nut to hold it in place. Grabbed a new Tool craft BCG and got to checking. Here is what it looks like fully forward with me pushing the firing pin. Firing pin easily reaches, lugs are fully locked up. Notice how far back the carrier is in the ejection port.

Here you can see full lug contact and firing pin protrusion.

I removed the BCG and reinserted it with me pushing the firing pin and a brass punch on the bolt face covering the firing pin hole. I did this to ensure the bolt/carrier would stop traveling before the firing pin protrudes.

Now note the bolt lugs in the next pictures. They are still making full contact and the firing pin IS NOT protruding. So even when the lugs have full contact, the firing pin cannot reach. The carrier still must move forward to fully push the bolt into the carrier. The bolt carrier can move rearward without turning the bolt because of the cam pin path in the carrier.

Next I pulled the carrier out as far as it can go before it touches the extension. In this position, the bolt cannot rotate because the cam pin it hitting the upper. The cam pin will not let the bolt to rotate until the cam pin gets to the cutout in the upper. If the bolt cannot rotate, the firing pin has 0 chance or reaching because the cam pin is going to keep the bolt from going into the carrier. Any further forward and the bolt cannot rotate because the lugs are in the way.
Note how far back the carrier is

This shows how parts that are in spec cannot cause an OOB discharge (in spec also means not broken).
A broken cam pin will certainly cause an OOB discharge. The bolt will go fully into the carrier without ever rotating the bolt.
A long firing pin or broken/short bolt tail will cause more firing pin protrusion but it would have to be extreme for it to reach the primer AND not have a fully rotated and locked up bolt.
A broken firing pin might have a newton cradle effect and be able to set off a primer.
A worn upper can also cause the bolt to rotate and collapse into the carrier enough for the firing pin to reach. The wear would have to be extreme for this to happen. You'd see the lugs in their entirety through the ejection port. In the following picture, the hammer will still hit the firing pin. Any further back and I don't think geometry will let that happen.

 

[chevy_man]

Looks like a pistol powder by mistake

H110 IS A PISTOL POWDER!

Never made any sub loads before I take it?

Another situation like Danilla_Ice's occurred last year when someone used CFE Pistol instead of CFE 223. The vendor shipped CFE Pistol and it went un-noticed by the reloader.

This is why reading comprehension is important. If you can't tell the difference between the word pistol and the numbers 223, you don't belong at a loading bench.

 

[M4orturnate]

H110 IS A PISTOL POWDER!

Never made any sub loads before I take it?





This is why reading comprehension is important. If you can't tell the difference between the word pistol and the numbers 223, you don't belong at a loading bench.

Semantics ever use h110 for 9mm dumbass. You cant blow up a 300blk with h110

 

[357Max]

OP @Southernspeed - I don't have quick load. I use GRT, it's free BTW so you may want to check it out.

They didn't have the Berry's in the bullet catalog so I used Hornady 220 RN 3090 with COAL set at 2.150"
The highest charge it would register pressure for H110 is 17.3gr @136,703psi. Beyond that it just said "you'll shoot your eye out kid"
Simulation below for 17.3gr charge. I played around with max load length & up to 18.3gr & any way I try it a max compressed load is over 100,000psi.

This could've easily been a double or near double charge of H110.

Out of battery is a BS theory. Didn't happen. Your protruded bent ejector retaining role pin is bent in the unlock direction. It was in battery when the event happened.

Case neck thickness could be a contributing factor, but it's unlikely the cause here. Neck thickness is all over the map for 300BO. I got sick of fighting neck thickness issue so I bought 500 Starline.

This could have been a number of issues stacked against you.

• Even if the trim length was correct, if shoulder was pushed back to far than as the 220gr slammed into battery, the neck may have hit the end of the chamber & thus crimped into bullet preventing normal release.
• Thick necks could have also hampered normal release.
• Powder selection H110
  • Room for possible double charge
  • Low case fill + magnum primer (#41's are the hotter than cci 450 IME). combine this with possible bullet release issues and the environment is ripe for detonation.
• No one has mentioned this yet, but I see a secondary chamfer on your barrels chamber. From what I see your chamber has less support at the .200 line than mine (BA 8.5 300BO). @Southernspeed - please drop a loaded round into your barrel & try to get a picture of how much case is exposed.

@Southernspeed - Obviously your upper & barrel are trash. I would replace the lower also. If the mag catch sits just a little lower than before you'll be fighting feed & bolt override issues. Not worth it.

I would also highly recommend Shooters World Socom powder for Subs instead of H110. The Socom was specialty formulated for this & It's excellent for supers also. With a full case it gives me 1875 with 155 eldm's from my 8.5" barrel. It's also my go to powder for 350 Legend.

 

[Southernspeed]

interesting. Did they go slower if you left the primer uncovered? Or faster?

From memory, way faster. Johnny’s Reloading Bench on YT had similar results during his 300 BO series when trying to make cheap, light subsonic plinking ammo.

OP @Southernspeed - I don't have quick load. I use GRT, it's free BTW so you may want to check it out.

They didn't have the Berry's in the bullet catalog so I used Hornady 220 RN 3090 with COAL set at 2.150"
The highest charge it would register pressure for H110 is 17.3gr @136,703psi. Beyond that it just said "you'll shoot your eye out kid"
Simulation below for 17.3gr charge. I played around with max load length & up to 18.3gr & any way I try it a max compressed load is over 100,000psi.

This could've easily been a double or near double charge of H110.

Out of battery is a BS theory. Didn't happen. Your protruded bent ejector retaining role pin is bent in the unlock direction. It was in battery when the event happened.

Case neck thickness could be a contributing factor, but it's unlikely the cause here. Neck thickness is all over the map for 300BO. I got sick of fighting neck thickness issue so I bought 500 Starline.

This could have been a number of issues stacked against you.

• Even if the trim length was correct, if shoulder was pushed back to far than as the 220gr slammed into battery, the neck may have hit the end of the chamber & thus crimped into bullet preventing normal release.
• Thick necks could have also hampered normal release.
• Powder selection H110
  • Room for possible double charge
  • Low case fill + magnum primer (#41's are the hotter than cci 450 IME). combine this with possible bullet release issues and the environment is ripe for detonation.
• No one has mentioned this yet, but I see a secondary chamfer on your barrels chamber. From what I see your chamber has less support at the .200 line than mine (BA 8.5 300BO). @Southernspeed - please drop a loaded round into your barrel & try to get a picture of how much case is exposed.

View attachment 8287370View attachment 8287373

@Southernspeed - Obviously your upper & barrel are trash. I would replace the lower also. If the mag catch sits just a little lower than before you'll be fighting feed & bolt override issues. Not worth it.

I would also highly recommend Shooters World Socom powder for Subs instead of H110. The Socom was specialty formulated for this & It's excellent for supers also. With a full case it gives me 1875 with 155 eldm's from my 8.5" barrel. It's also my go to powder for 350 Legend.
View attachment 8287329
View attachment 8287386View attachment 8287388

that’s great info, scary but great. That’s some serious pressure. I’m still leaning toward a double charge but not sure how I managed to do that!
Thanks for taking the time for such an in depth reply.

 

[357Max]

From memory, way faster. Johnny’s Reloading Bench on YT had similar results during his 300 BO series when trying to make cheap, light subsonic plinking ammo.

that’s great info, scary but great. That’s some serious pressure. I’m still leaning toward a double charge but not sure how I managed to do that!
Thanks for taking the time for such an in depth reply.

This shows the single angle chamfer on mine.

Hard to get a pic with case in but this is a similar perspective to your pic. It’s not a huge difference, but I like to have as mch support as possible near the case head. Possibly a contributing factor, sure but all signs point to overpressure event.

If I were in your shoes I’d switch powder, batch brass into lots of same head stamp, make sure trim length leaves at least .010-.015 more clearance than shoulder head space., measure neck OD of loaded factory round & do not exceed on reloads, & make sure bullet drops into neck on fired rounds.

Now about that wicked flinch you’ve developed
Glad you didn’t get injured.

 

[Southernspeed]

This shows the single angle chamfer on mine.
View attachment 8287449
Hard to get a pic with case in but this is a similar perspective to your pic. It’s not a huge difference, but I like to have as mch support as possible near the case head. Possibly a contributing factor, sure but all signs point to overpressure event.

If I were in your shoes I’d switch powder, batch brass into lots of same head stamp, make sure trim length leaves at least .010-.015 more clearance than shoulder head space., measure neck OD of loaded factory round & do not exceed on reloads, & make sure bullet drops into neck on fired rounds.

Now about that wicked flinch you’ve developed
Glad you didn’t get injured.
View attachment 8287457

I loaded up some subs with 1680 yesterday for my Ruger Ranch. They were fine. I just went online to buy some SBR- Socom as you suggested but of course …. everyone is out of stock ( apart from the scammers!)
Thanks again for the info. That’s settled me on a double charge. Stupid mistake ( still can’t figure how I did it) but at least I can be more vigilant.
I got off light from this one. Wrist was sore for a few days but I still have all my fingers and my good looks of course

 

[357Max]

I loaded up some subs with 1680 yesterday for my Ruger Ranch. They were fine. I just went online to buy some SBR- Socom as you suggested but of course …. everyone is out of stock ( apart from the scammers!)
Thanks again for the info. That’s settled me on a double charge. Stupid mistake ( still can’t figure how I did it) but at least I can be more vigilant.
I got off light from this one. Wrist was sore for a few days but I still have all my fingers and my good looks of course

Only 2 lbs left in stock here.

Shooters World Powder SBR Socom - 1lb | Bruno Shooters Supply

www.brunoshooters.com

 

[Southernspeed]

Only 2 lbs left in stock here.

Shooters World Powder SBR Socom - 1lb | Bruno Shooters Supply

www.brunoshooters.com

Thanks!

 

[cas6969]

You cant blow up a 300blk with h110

You can sure blow the primer out of them though.

 

[Southernspeed]

This shows the single angle chamfer on mine.
View attachment 8287449
Hard to get a pic with case in but this is a similar perspective to your pic. It’s not a huge difference, but I like to have as mch support as possible near the case head. Possibly a contributing factor, sure but all signs point to overpressure event.

If I were in your shoes I’d switch powder, batch brass into lots of same head stamp, make sure trim length leaves at least .010-.015 more clearance than shoulder head space., measure neck OD of loaded factory round & do not exceed on reloads, & make sure bullet drops into neck on fired rounds.

Now about that wicked flinch you’ve developed
Glad you didn’t get injured.
View attachment 8287457

Actually I’ve just noticed my barrel is/was an Aero Precision barrel but I’ve no idea who makes theirs ( unless they do? )

 

[357Max]

Actually I’ve just noticed my barrel is/was an Aero Precision barrel but I’ve no idea who makes theirs ( unless they do? )

I think Aero are Ballistic advantage.

 

[chevy_man]

Semantics ever use h110 for 9mm dumbass. You cant blow up a 300blk with h110

I use it in 357 mag. There's far more pistols than 9mm, although just about everything has data in 9mm. Your brilliant analysis of "you used a pistol powder" when the op stated that he used H110 is amazing. You should write a book or two for the rest of us to learn!

And yes, you can. Obviously.

I also used lots of pistol powders to make sub loads. I now generally use cfe black because it has a lower density, and can't be double charged.

 

[alamo5000]

I was specifically responding to that post. I don’t see a bolt in the extended, fully-forward position.

That's easy because none of the pictures show one in the fully forward position. It shows the positions of the bolt where the firing pin is completely exposed to the primer. Anything forward of that would either be a not exposed firing pin, or for a split second, a partially exposed firing pin.

In those pictures, both positions and everything in between allow the firing pin to be fully exposed to the primer.

It still goes back to what I was saying all along. An out of spec case gets stuck in the chamber, thus prematurely forcing the bolt rearward. At that same time the bcg is still moving forward so it's trying to seat the bolt all the way in, except it can't. The lugs on the bolt are twisting and turning laterally against the lugs on the barrel extension.

This friction slows everything down, but as soon as the lugs on the bolt clears the lugs on the barrel extension all of that tension gets instantly released before the bolt can fully turn into place.

The bolt doesn't have to be fully seated into the carrier for the firing pin to contact the primer as noted in my pictures. That applies to any bolt carrier group from any manufacturer.

 

[alamo5000]

In case you were still wondering, I took a barrel extension off a shot out Noveske barrel and put it in a spare upper I have so I can test the OOB firing. Plus side is no barrel blocking the view.
Warning: long winded post coming.
Cliffs: parts in spec can't cause an OOB discharge.

I put the Noveske extension in the new upper and threw on a barrel nut to hold it in place. Grabbed a new Tool craft BCG and got to checking. Here is what it looks like fully forward with me pushing the firing pin. Firing pin easily reaches, lugs are fully locked up. Notice how far back the carrier is in the ejection port.
View attachment 8286449


Here you can see full lug contact and firing pin protrusion.
View attachment 8286450



I removed the BCG and reinserted it with me pushing the firing pin and a brass punch on the bolt face covering the firing pin hole. I did this to ensure the bolt/carrier would stop traveling before the firing pin protrudes.
View attachment 8286451

Now note the bolt lugs in the next pictures. They are still making full contact and the firing pin IS NOT protruding. So even when the lugs have full contact, the firing pin cannot reach. The carrier still must move forward to fully push the bolt into the carrier. The bolt carrier can move rearward without turning the bolt because of the cam pin path in the carrier.
View attachment 8286452

Next I pulled the carrier out as far as it can go before it touches the extension. In this position, the bolt cannot rotate because the cam pin it hitting the upper. The cam pin will not let the bolt to rotate until the cam pin gets to the cutout in the upper. If the bolt cannot rotate, the firing pin has 0 chance or reaching because the cam pin is going to keep the bolt from going into the carrier. Any further forward and the bolt cannot rotate because the lugs are in the way.
Note how far back the carrier is
View attachment 8286479
View attachment 8286480

This shows how parts that are in spec cannot cause an OOB discharge (in spec also means not broken).
A broken cam pin will certainly cause an OOB discharge. The bolt will go fully into the carrier without ever rotating the bolt.
A long firing pin or broken/short bolt tail will cause more firing pin protrusion but it would have to be extreme for it to reach the primer AND not have a fully rotated and locked up bolt.
A broken firing pin might have a newton cradle effect and be able to set off a primer.
A worn upper can also cause the bolt to rotate and collapse into the carrier enough for the firing pin to reach. The wear would have to be extreme for this to happen. You'd see the lugs in their entirety through the ejection port. In the following picture, the hammer will still hit the firing pin. Any further back and I don't think geometry will let that happen.
View attachment 8286571

This is good information but it doesn't show the full extent of the sequence of actions that lead to the OOB detonation.

 

[M4orturnate]

I use it in 357 mag. There's far more pistols than 9mm, although just about everything has data in 9mm. Your brilliant analysis of "you used a pistol powder" when the op stated that he used H110 is amazing. You should write a book or two for the rest of us to learn!

And yes, you can. Obviously.

I also used lots of pistol powders to make sub loads. I now generally use cfe black because it has a lower density, and can't be double charged.

If we're going to be nit picky its a magnum pistol powder. I dont think a double charge can do that to a gun and at mag length i dont think you can fit more then a double charge.

 

[chevy_man]

If we're going to be nit picky its a magnum pistol powder. I dont think a double charge can do that to a gun and at mag length i dont think you can fit more then a double charge.

Keep thinking. Less than a double was shown to be roughly 137k psi.

 

[Southernspeed]

If we're going to be nit picky its a magnum pistol powder. I dont think a double charge can do that to a gun and at mag length i dont think you can fit more then a double charge.

Going by the GRT model posted above, at over 4 times the normal pressure for that round , I reckon it could easily do the damage seen.

 

[srt-4_uk]

This is good information but it doesn't show the full extent of the sequence of actions that lead to the OOB detonation.

I pulled the carrier all the way back, pushed on the bolt face to "prematurely force the bolt rearward". But the bolt can't go far enough back without turning because of the cam pin and cam path in the carrier won't let it. The bolt MUST turn FULLY for the firing pin to reach past the bolt face.
If there's another sequence you'd like me to try, I'd be happy to.

 

[M4orturnate]

Going by the GRT model posted above, at over 4 times the normal pressure for that round , I reckon it could easily do the damage seen.

If thats the case then im wrong. Im curious how close the model is. 130+ will tear stuff up.

 

[alamo5000]

I pulled the carrier all the way back, pushed on the bolt face to "prematurely force the bolt rearward". But the bolt can't go far enough back without turning because of the cam pin and cam path in the carrier won't let it. The bolt MUST turn FULLY for the firing pin to reach past the bolt face.
If there's another sequence you'd like me to try, I'd be happy to.

First I would like to state that having an OOB detonation is actually not that easy. It is possible, but just not easy to do.

Any 'test' would have to have all of these factors going on at once. Enough rearward force to try and push the bolt rearwards while the entire carrier is still in full forward momentum.

The teeth on the bolt need to push laterally against the teeth on the barrel extension to the point where it creates sufficient friction from the pre mature twist of the bolt.

THEN after that set of specific conditions are met, the bolt still needs to travel forward until the teeth on the bolt just barely clear the forward edge of the teeth on the extension.

At that specific moment in time all of the force from the forward momentum and various friction points would release. Instead of gently turning into place it will 'release' and snap over.

Think about this non related example. Imagine if you had a nut that was stuck on a bolt that was attached to something solid. With a regular wrench you can't get the bolt loose so you get a cheater bar. So now you put tremendous force on that stuck bolt but right at that moment it breaks loose while it's still under heavy torque.

In essence that's the same concept. It will be extremely difficult to recreate that by just hand maneuvering parts together.

It's not easy to create in the first place but it certainly can happen.

 

[Southernspeed]

If thats the case then im wrong. Im curious how close the model is. 130+ will tear stuff up.

I reckon even if it’s out by 10-20% I’d have no desire to try it again

 

[srt-4_uk]

First I would like to state that having an OOB detonation is actually not that easy. It is possible, but just not easy to do.

Any 'test' would have to have all of these factors going on at once. Enough rearward force to try and push the bolt rearwards while the entire carrier is still in full forward momentum.

The teeth on the bolt need to push laterally against the teeth on the barrel extension to the point where it creates sufficient friction from the pre mature twist of the bolt.

THEN after that set of specific conditions are met, the bolt still needs to travel forward until the teeth on the bolt just barely clear the forward edge of the teeth on the extension.

At that specific moment in time all of the force from the forward momentum and various friction points would release. Instead of gently turning into place it will 'release' and snap over.

I get what you are saying but if the bolt is not fully locked up, the firing pin will not reach. Look at the cam pin path in the carrier. There's a reason the angle is so sharp to rotate but the travel is so long. You can go from full firing pin protrusion to no pin protrusion, all without the bolt unlocking as shown in the previous set of pictures.
Below is a picture of Partial lock up. bolt barely rotated with me pushing the firing pin all the way forward. notice the firing pin is no where close. Any more I push the carrier, the bolt will continue to rotate only exposing the firing pin after it's fully locked up.

If you want to pay shipping and promise to return it, I'll send you this extension and you can see for yourself with an upper and an extension instead of just a BCG on a table. You can see how everything works together to prevent what you are talking about.
I'll get some oversized brass and run the same test in a barrel but I already know what gonna happen because I've done it already (accidentally). It just ends in rounds that don't fire and you have to mortar them out because the case is wedged in the chamber.

 

[hlee]

At this point, this argument about the firing pin is the the VCR discussion scene from City Slickers.