How to blowup your rifle

Winkfish

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Sep 27, 2016
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182
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Wisconsin
I did size each case. I have provided a failed case and one that I pulled the bullet out of with the charge in questions to BignGreen for his analysis. I am willing to let an objective measurement of that case to determine if the sized case was out of specifications as well.
 

McDoone

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Dec 14, 2009
Messages
9
5RWill,
I’m too old and have had too much experience to discount any argument out of hand. But a considerable amount of my experience has been in the conditions described. I’ve spent years carrying a rifle in the cold, jumping in and out of vehicles, hunting, competing, and testing ammo in much the same way as described. In fact most of us who hunt and shoot above the 49th parallel have done the same. Without going into the science of it, which I’d have to leave to someone else anyway, I’m pretty confident that’s not the explanation or I’d have to give up hunting!!! After the first moisture post, I pretty much skipped the rest, but if some of posters come back to this, I might visit it again.
 

WildRose

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I did size each case. I have provided a failed case and one that I pulled the bullet out of with the charge in questions to BignGreen for his analysis. I am willing to let an objective measurement of that case to determine if the sized case was out of specifications as well.
That's the problem, once the case has been fired we really have no way to look backwards and see what the pre firing dimensions where.

If the neck was over length though he should probably be able to see evidence of crimping on the end.

I ran into something similar many moons ago with a .220 swift. I had inadvertantly skipped case trimming on one batch which I routinely did before resizing just to ensure having a small threshold of safety.

I didn't blow the gun up but I sure blew the primer right through and blew smoke and hot gas out of every orifice in the rifle.

Scared the snot out of me.
 

5RWill

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Oct 30, 2016
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Mississippi
5RWill,
I’m too old and have had too much experience to discount any argument out of hand. But a considerable amount of my experience has been in the conditions described. I’ve spent years carrying a rifle in the cold, jumping in and out of vehicles, hunting, competing, and testing ammo in much the same way as described. In fact most of us who hunt and shoot above the 49th parallel have done the same. Without going into the science of it, which I’d have to leave to someone else anyway, I’m pretty confident that’s not the explanation or I’d have to give up hunting!!! After the first moisture post, I pretty much skipped the rest, but if some of posters come back to this, I might visit it again.

Yeah as i said i'm not saying it was the issue, i explicitly stated such. Was just offering a premise as to how condensation could occur in the chamber, of course i was asking. Though admittedly should've taken it to PM as the thread has enough guestimation and filler as is.
 

Winkfish

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Wisconsin
Is it not fair to assume that one would be able to measure one of the un-fired cases and compare its dimensions to the known specifications. If the un-fired case is out of spec it would aid in supporting your comments?


That's the problem, once the case has been fired we really have no way to look backwards and see what the pre firing dimensions where.

If the neck was over length though he should probably be able to see evidence of crimping on the end.

I ran into something similar many moons ago with a .220 swift. I had inadvertantly skipped case trimming on one batch which I routinely did before resizing just to ensure having a small threshold of safety.

I didn't blow the gun up but I sure blew the primer right through and blew smoke and hot gas out of every orifice in the rifle.

Scared the snot out of me.
 

phorwath

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Apr 4, 2005
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7,283
Location
Alaska
The elastic yield strain for brass cases is low enough that most of us exceed it while working up to maximum pressure loads.
The elastic yield limit for the steel and brass is exceeded whenever the steel or brass has permanently deformed under tensile force.
I measure case expansion just forward of my cartridge rims while developing loads. When I measure 0.0005" or more expansion after firing a new casing, I accept that as a maximum load. The permanent expansion also means the case pressure developed tension/strain in the case head which exceeded the elastic yield strain of the brass case head.

In other words, the elastic strain limit for the brass casing provides little value in determining a minimum case pressure that could excite any of us. We commonly exceed it during load work up. Primer pocket expansion? Again it means the elastic yield limit of the case has been exceeded.
Whether or not permanent deformation occurs is based on two factors: 1) the modulus of elasticity of the metal and 2) the thickness or cross sectional area of the metal material.

If there's an engineer that's more up on their mechanics of materials education/knowledge than I, feel free to refine this explanation closer to dead nutz on. I believe the above to be correct, or I wouldn't have just posted it.

If the above explanation doesn't make sense, another way to view this is the brass casing IS the pressure relief valve that typically limits the reloader's operating pressure and MV. It's the safety relief valve that helps protect us from cataclysmic rifle blowups, provided we use a little bit of common sense. When the brass case head expands, when the case head flows into the plunger or extractor grooves in the bolt face, when the primer pockets enlarge, and when we experience stiff bolt lifts, the elastic strain limits of the case head have been exceeded and we typically take our foot off the accelerator. We stop adding additional gun powder.

The weakest pressure containing link in our rifles is the primer and the unsupported brass case head area. Those should always yield to permanent deformation before a properly designed sporting rifle action fails. That weakness is due to the much lower modulus of elasticity of the brass, combined with the relative thinness of the brass case head area. It prevents us from casually running operating pressures anywhere near the pressures required to set back the steel bolt lugs or permanently expand/deform the steel barrel.

Back in the late 70s, early 80s, overambitious individuals manufactured steel case heads which could be threaded onto the remainder of the forward portion of the casing, which was made of brass. The unsupported case head was steel, the chamber supported portion of the case was brass. The intent was to increase operating pressure and MV, as the steel case head has a much higher strength (modulus of elasticity - elastic yield value). It was also a recipe for increased catastrophic rifle action/barrel blowups. Because now the operating pressures could be increased to a level much closer to those levels required to blow up the rifle. But there was still the weak link. That being the primer. A pierced primer would still torch the bolt face. That fad came and went. No doubt for the best. That degree of over-ambitiousness probably led to physical harm, bankruptcy, natural selective evolutionary removal from the gene pool... Whatever the reasons, the fad came and went.
 
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WildRose

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Is it not fair to assume that one would be able to measure one of the un-fired cases and compare its dimensions to the known specifications. If the un-fired case is out of spec it would aid in supporting your comments?
There's no way the fired case will be at it's original pre fired dimensions. Measuring other unfired cases can only tell you their dimensions, not the dimensions of the case in question.

The numbers he's already given us tell us it's currently way out of spec due to the excessive pressures.
 

McDoone

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Joined
Dec 14, 2009
Messages
9
5RWill
As far as I’m concerned your question was entirely valid. And your experience is in very different conditions than I have with different equipment.
This thread is making me think about one of my own experiences and wonder if I came to the wrong conclusion.
Given the description of Winkfish’s loading practice (which is very good, in my opinion) I think that we might never know what caused the event. We are left with the evidence and we can analyze that, and if something in the rest of the loaded ammo or rifle barrel shows up that we can point at and say “aha” we can blame it on that. But failing that and without being able to scientifically trace the actual original event and examine the original unfired round we are going to be left with a best guess.
So guesses are a pretty good thing, I think. And the incredible amount of interest this topic has generated in a very short time has resulted in posts that gave me some new and I feel valid information.
 

smoked

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Jan 8, 2011
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NORTH EASTERN NEVADA
Something is off, I dont believe retumbo would produce that velocity with a 26 inch stick and the load only be around 87 grains. I overload and push these rums quite often from -20 through 110 and have never seen anything like that. Maybe a machining issue with the rifle or bad (scale)s. 90gr retumbo with a 230 should be around 3k. Strange the day before it was fine but is it possible to have been weakened the day before plus the brittleness of the cold tightened the bore?
 

McDoone

Member
Joined
Dec 14, 2009
Messages
9
If the above explanation doesn't make sense, another way to view this is the brass casing IS the pressure relief valve that typically limits the reloader's operating pressure and MV. It's the safety relief valve that helps protect us from cataclysmic rifle blowups, provided we use a little bit of common sense. When the brass case head expands, when the case head flows into the plunger or extractor grooves in the bolt face, when the primer pockets enlarge, and when we experience stiff bolt lifts, the elastic strain limits of the case head have been exceeded and we typically take our foot off the accelerator. We stop adding additional gun powder.

The weakest pressure containing link in our rifles is the primer and the unsupported brass case head area. Those should always yield to permanent deformation before a properly designed sporting rifle action fails. That weakness is due to the much lower modulus of elasticity of the brass, combined with the relative thinness of the brass case head area. It prevents us from casually running operating pressures anywhere near the pressures required to set back the steel bolt lugs or permanently expand/deform the steel barrel.

Back in the late 70s, early 80s, overambitious individuals manufactured steel case heads which could be threaded onto the remainder of the forward portion of the casing, which was made of brass. The unsupported case head was steel, the chamber supported portion of the case was brass. The intent was to increase operating pressure and MV, as the steel case head has a much higher strength (modulus of elasticity - elastic yield value). It was also a recipe for increased catastrophic rifle action/barrel blowups. Because now the operating pressures could be increased to a level much closer to those levels required to blow up the rifle. But there was still the weak link. That being the primer. A pierced primer would still torch the bolt face. That fad came and went. No doubt for the best. That degree of over-ambitiousness probably led to physical harm, bankruptcy, natural selective evolutionary removal from the gene pool... Whatever the reasons, the fad came and went.
Got some of those when they originally became available, fired one shot, no ill effects, but came to my senses for all the above reasons! Sometimes good luck works in my favour.
 

GelatinousPig

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Dec 15, 2015
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Location
Missouri
Is it possible there was moisture of some form introduced during the powder loading process for the culprit cartridge? If the powder froze together in certain areas, couldn't that be (in theory) a cause for S.E.E. to occur? Hot coffee steaming next to the powder scale perhaps?
 
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phorwath

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Consequently, confirmation that the inner diameter of the barrel chamber/bore swelled/bulged means that the elastic strain limits of the steel were exceeded. Confirming mooch-o (much) pressure.
 

learning

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Apr 24, 2009
Messages
225
Consequently, confirmation that the inner diameter of the barrel chamber/bore swelled/bulged means that the elastic strain limits of the steel were exceeded. Confirming mooch-o (much) pressure.

Does this mean you don’t buy into the caffeinated retumbo theory?
 

phorwath

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Messages
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Alaska
Does this mean you don’t buy into the caffeinated Retumbo theory?

Hah... :) More or less... :D

Maybe Hodgdon slipped a little solid rocket fuel from the former space shuttle boosters into this Lot of powder. Maybe some anti-matter. Black hole sorta stuff.
 

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