Accidental discharge with open bolt

[baboonstalker]

I was taking part in a world championship shoot when my AII based competition rifle discharged before the locking lugs engaged. It was on the third range of the second day of competition. I opened the bolt (fairly hard) after the first shot. Something felt strange when the bolt hit the bolt stop, but when I fed the next round (single shot) the bolt would not close all the way. Being under time constraints of 90 seconds/ 5 shots, I shoved the bolt forward and the shot went off before the bolt reached the forward position.
My stock blew to pieces, the bolt shot backwards against my hand and past my arm.
The extractor blade was recovered 10m behind me, the bolt 30m behind me and the extractor and a piece of brass was surgically removed in theatre from my hand later that night.
I suspect that the bolt de-cocked when it hit the bolt stop on the previous cycle, but how can the primer be set off without the round ever hitting the front of the chamber?

I count myself very lucky to have escaped more serious injury to myself or any bystanders, but I would like to know why this happened. I had my other competition rifle (L579) de-cock while cycling and had the notch cut a little deeper to prevent it from happening.

Sako flags were flying at the firing point on the day and the first prize for the world champ was a new Sako rifle.

Anybody have any idea of what might have happened here??

 

[kevinlg]

Has the bolt/bolthandle been reworked/modified in any way?

I ask because your pic of the bolt does not "look" quite right.

Thanks

 

[gunner620]

I suspect that the trigger was either modified or adjusted too light and the firing pin de-cocked prematurely. Just my guess ! Another possibility is the pin that retains the trigger on the receiver may have loosened and was only holding on one side causing misalignment of the cocking piece to the trigger. Just my two cents. Sorry about your injury and rifle. Jim

 

[baboonstalker]

Kevin, The bolt knob was machined down to fit a "tactical style" knob. Due to the girth of the stock, too little of the original bolt handle protruded past the stock making it a fingery job to cycle the bolt. The bend in the bolt handle is due to the impact with my hand as the bolt flew back. I had a clean spot on my hand where the knob was, while the rest of my hand was covered with powder residue.

The trigger was not set light at all and the engagement was good. The action still cocks and fires after the event and you can hit the tang on a poly urathane block without the rifle de-cocking or firing. I consider the trigger set-up to be above suspicion, but am open to change my opinion should evidence proves otherwise.

The fact that the bolt did not close normally still points to the bolt being de-cocked (turned) so the firing pin catch was not riding in its guide or some other issue.

 

[gunner620]

baboonstalker, that's a strange incident indeed. Perhaps something changed the firing pin adjustment as the firing pin must have been protruding when the bolt was pushed home. You indicated the bolt lugs were not engaged when the rifle discharged. I think I would look there. I am no expert and strange things can happen, very unfortunate. Let us know what you find. Jim

 

[enotstehw]

Do you have the empty case of the first round? It may be able to tell you something.

 

[tslans]

High primer?

 

[baboonstalker]

High primer - I don't think so, I checked the remaining rounds and none of them proud. Primer pockets have been "uniformed" and cleaned. I seat my primers on the press and am pretty confident that primer was not proud.

Removed the case from the chamber this morning and looking at the shoulder and neck, the round was still 0.0244" from the front of the chamber when the round detonated. I bumped the shoulders back 0.001" before loading. Bullets are seated "kissing the lands" and necks are turned to allow 0.004" clearance with bullet seated.

Firing pin is 0.267" from the bolt face when cocked, protruding 0.050" when de-cocked.

I do not have the previous case at hand, but the bullet was delivered to the target dead-on. Someone might have recovered the case, I will check.

Thank you for the help so far

 

[kevinlg]

Ok then......so your pic shows the bolt in the cocked position, with it's handle bent forward. Assuming that this was its position(cocked) at detonation......it should not be possible for the firing pin tip to reach the boltface, due to hitting the boltsear cocking ramp.

I would be looking real hard for your first fired round case. I think "something" was left behind on the boltface, i.e. maybe the blanked disc of a failed primer. So.......attempting to force the bolt forward, before rotating the bolthandle down, indents the primer face of the second round.......and boom!

Hope this helps.

 

[baboonstalker]

Ok then......so your pic shows the bolt in the cocked position, with it's handle bent forward. Assuming that this was its position(cocked) at detonation......it should not be possible for the firing pin tip to reach the boltface, due to hitting the boltsear cocking ramp.

I would be looking real hard for your first fired round case. I think "something" was left behind on the boltface, i.e. maybe the blanked disc of a failed primer. So.......attempting to force the bolt forward, before rotating the bolthandle down, indents the primer face of the second round.......and boom!

Hope this helps.

The bolt was picked up in the de-cocked state. i will look for the case.

 

[paulsonconstruction]

Been scratching my head watching this thread & wondering what the heck happened. I think Kevinig has the best explanation, as it is impossible for your bolt to de-cock or the firing pin to protrude unless the bolt handle is fully lowered. Had to be something on the bolt face, which is why it wouldn't close. You said "something felt strange" when the previous round hit the bolt stop/ejector, which could be an indicator of something stuck on the bolt face, like a piece of primer possibly. Like said, the brass from the previous round probably holds the answer.

 

[baboonstalker]

I have asked around, but it would seem that the last "good" case was not recovered by myself or any of my friends from the shooting position.

I have re-assembled the rifle to go through the whole sequence again and i think I now have a good explanation of what happened:

I was shooting the third of six ranges on the second day of competition when the accident happened. Shooting from the sitting position at the time, I was sitting flat on the ground with the target on my 9 O'clock. My left leg in an upright position and my right leg folded and flat on the ground.

Opening the bolt fairly hard after my first shot, the bolt hit the bolt stop at the back of it's stroke and I felt something different. At this point the cocking piece might also have made contact with the stock. In any case, I suspect it was at this point that the bolt de-cocked.
I placed a new round on the magazine follower and proceeded to close the bolt. It became evident fairly early on that something was holding the bolt back and it did not slide all the way forward freely. Thinking that it might be some foreign matter (grass) obstructing the bolt or the bolt-stop that swung out of position/ extractor blade that bent, I gave the bolt a sharp rap with the palm of my right hand. Up to this point I had a clear view of the loaded round and could see that it was free and not the cause of the "jam"
The rap to the bolt moved the whole rifle forward (the bolt might also have advanced a small distance forward in the action), while the inertia of the round caused it to stay still. The firing pin was protruding from the bolt at this time and when it hit the primer, the primer ignited.

The explosion of the primer shot the round forward, the primer backwards and ignited the powder charge. As pressure built up inside the case, the jet of gas shooting out the primer pocket would also have "rocketed" the bullet, case and powder charge forward as a unit. As the bullet struck the lands and pressure built up inside the case, the case would now be shoved backwards momentarily until the expansion of the case against the chamber walls would lock it in position. The pressure was now sufficient to push the bullet through the barrel and to blow the head of the case off.

The rearward explosion hit the bolt with only a small space to vent through the loading port. The bolt was now propelled backwards, while gas entered the magazine box. Blowing sideways, it destroyed the stock and in a downward direction, it bent the bottom metal and blew open the floor plate.

The velocity of the expanding gas or the case head striking the bolt face dislodged the extractor and sent it flying into my hand.

All things considered, I feel very lucky that nobody suffered serious or permanent injury.

 

[topgear]

Hi Baboonhunter

I still find a couple of things hard to understand.

1. How could the force of just your hand bend the bolt handle back that much? Or is it a case it hit on something hard other than your hand when it came flying back?

2. Can the extractor hold the case on enough without the bolt engaged to allow a detonation or was the cartridge hitting on something to allow it to be held on the bolt face?

3. If the bolt de-cocked on ejection of the last round there is no way the bolt would have gone back in the action? Just look at the number of threads on this forum titled "Help my bolt won't got back in my rifle" after a newbie takes the bolt out of his rifle and somehow de-cocks his bolt.


Anyway mate your pretty lucky. I thought it was only Blasers that blew up!

 

[baboonstalker]

Hi Topgear,
It's all hard to understand, but i have to make sense of it. I ofn 3 other Sako's and unless i clear this up good and proper in my mind, i might just pick up a nasty flinch!

1. the bolt handle was bent on my palm as the bolt shot backwards. Had the nice clean spot there while the rest of my hand was covered in powder residue.

2. case was lying free on the magazine follower. forward motion of the rifle/ bolt and inertia of the loaded round is all that was involved here.

3.The bolt goes into the action in the de-cocked state and gets stuck +- 35mm from the locked position. That strokes with the (last) image I have engraved in my brain from the rifle on the day.

By the way, there was a team from Aussie taking part as well!
Lucky? you tell me. Every time I re-enact the "event" i can not help but observe that the extractor was aimed straight at my eye/head and i was just lucky to catch it with my hand. If this happened on a prone range, or if someone was standing behind me, the outcome could have been very different.

cheers mate
Pieter

 

[paulsonconstruction]

Two things I'm fairly certain of. No way your palm bent the bolt handle, otherwise you would have multiple fractures in your hand & no way your rifle "decocked" & your firing pin was protruding with the bolt handle in the raised position. Most likely the bolt handle caught on the action recess & was bent prior to hitting your hand. What exactly happened I can't say, but it's most likely something was stuck on your bolt face from the previous round that caused the primer to go off prematurely in the following round. The mechanics of the bolt just won't let what you say happen unless something is "broken" in the bolt. Did you check the innards of the bolt to see if anything is broken that would allow it to "decock" as you claim. The bolt being picked up in the decocked state is understandable as the only thing that keeps it in a cocked state is the bolt/trigger sear engagement after it is closed. Going thru that violent experience could easily leave it in the decocked state as you can do that with a flick of the wrist on a bolt that is out of an action.

 

[topgear]

Did the projectile go down the barrel? Is it possible the cartridge hit the barrel shank i.e. didn't feed into the chamber so you where able to detonate it with your de-cocked bolt?

Its possible, but you would have had to give it a fair rap with your hand to do it I would imagine.

 

[stonecreek]

It is simple to decock your bolt to illustrate that a decocked bolt won't go very far into the action. I think that theory is out. However, a broken firing pin lodged in the forward position (admittedly an unlikely situation) could conceivably cause the phenomenon.

While it is impossible to diagnose such a catastrophic failure from 5,000 miles away, the theory that some type of foreign matter (perhaps a shred of a blown primer) adhered to the bolt face and cause the premature ignition of the subsequent round seems the least implausible, among all the implausible possibilities.

A severely out-of-spec, overly sensitive primer in the offending round might have been ignited merely by the force of the bolt on the cartridge head, but I've never seen a primer do this and think that the possibility is extremely unlikely.

Perhaps you could write to Mythbusters to see if they can replicate it.

 

[baboonstalker]

Paul and others,
I could feel the bolt being restricted while still having a good view of the round. I could see that the round was free and not the source of the obstruction. With the bolt in the open position it is quite possible to de-cock the bolt and i have done this many times since to prove that it is a possible scenario. It also duplicates the "feel" of the jam I experienced, as it gets stuck in the right place and it is not a dead stop, but rather a jam with a little bit of give in it.

I can rule out the possibility of something stuck to the bolt face, as this would allow the bolt to move almost all the way to the forward position, obstruct the view of the round and hold the round against the front of the chamber.

As far as the bent handle goes, this is of little importance as it happened after the fact and is merely the result and not the cause. My hand was exerting force on the handle at the moment of the explosion, so the bolt reversed the direction of movement of my hand. Since my hand was making contact with the bolt while it was still at rest, it accelerated with the bolt instead of the bolt connecting my hand at full speed. This probably saved me the fractures you described.

Bolt innards are still in tact, and if you cock the rifle it still fires. (dry fire of-course, I am not quite ready to fire anything live in it yet!)

@TG, I was feeding rounds "single shot" onto the magazine follower at the time. I could see that the round was free from obstruction and yes, the bullet did leave the barrel.

 

[enotstehw]

Pieter

I am assuming that you have been using your own reloads.
Try using an empty case with just a primer . . . and insert it into the chamber and with the bolt decocked . . . see if raming the bold against it will set off the primer.

 

[paulsonconstruction]

Pieter

I am assuming that you have been using your own reloads.
Try using an empty case with just a primer . . . and insert it into the chamber and with the bolt decocked . . . see if raming the bold against it will set off the primer.

A decocked bolt won't go in the action.