How to blowup your rifle

[Pdvdh]

I've been trying to find the psi where cartridge brass suffers plastic deformation, that would at least give us an idea of a min pressure this reached. It also seems to me this would have taken some time under pressure as well not just a spike.

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.

 

[Timeout]

Winkfish

I've read the whole thread and I am convinced that the engineers at Remington did a very good job designing your gun.

I don't think that the fouling of the barrel is the culprit, I think the whole event took place while the projectile was still in the chamber as once the bullet travels down the bore pressure drops dramatically.

The unusual location of the case separation stretch mark as seen in post #50 points to the lubricant in the chamber or on the case.
Good gun design !!! as the lugs sustained the whole brunt of the charge with a lubricated (well, half of it) case in the chamber.

I suspect that the case was loaded for the 190gr projectile and when 230gr was seated to the same COL, the projectile reduced further the powder space sending the pressure higher still. There is 180 thou difference in length between those two projectiles.

On your original photo in post #1 the bolt head bears hammering marks on its lip, why did you hammer there.

I'm not suggesting that lubricant on the brass alone caused this problem. I do believe that lubricant left on the brass prevents the cartridge case from "grabbing onto" the chamber wall when firing. This can cause the case to slam rearward into the bolt. Usually not terribly problematic if the chamber is properly head spaced, and brass not excessively shortened from base to shoulder during resizing. I am suggesting that I think lubricant left on the cartridge case or chamber walls is not desirable.

 

[RockyMtnMT]

I'm not suggesting that lubricant on the brass alone caused this problem. I do believe that lubricant left on the brass prevents the cartridge case from "grabbing onto" the chamber wall when firing. This can cause the case to slam rearward into the bolt. Usually not terribly problematic if the chamber is properly head spaced, and brass not excessively shortened from base to shoulder during resizing. I am suggesting that I think lubricant left on the cartridge case or chamber walls is not desirable.

I agree. A lubed case will show false pressure signs. It does not increase the pressure.

Steve

 

[Pdvdh]

Lubricating the chamber or exterior of a casing will increase the setback force applied to the bolt head.
But I can assure you that the engineers that designed the action determining the structural design for their action did not include the cartridge casing as any offsetting factor in the design strength of their action.
Otherwise the action manufacturer would include a warning that the chamber and cartridge casing must be cleaned and free of any and all lubrication. And how much sense does that make, when we all use lubricants on our firearms for wear and corrosion reduction/protection?

It's a non-issue, of no consequence, in comparison to the end result when this cartridge was fired.

 

[Pdvdh]

I agree. A lubed case will show false pressure signs. It does not increase the pressure.

Steve

Exactly correct. It also increases the force applied to the bolt lugs. But only due to the loss of friction between the casing and the chamber sidewalls. The internal pressure is, however, no different.

 

[Pdvdh]

I also flat out dismiss condensation as any fact in this overpressure event. There's been so much speculative banter posted in this thread that elimination of these erroneous speculative causes would greatly narrow down the list of potentially real causes.

Otherwise we'd be just as well off throwing gum at the wall and studying which sticks and which falls to the ground.

 

[RockyMtnMT]

I also flat out dismiss condensation as any fact in this overpressure event. There's been so much speculation bandied about in this thread that elimination of these erroneous speculation would greatly narrow down the list of possible causation factors.

I the condensation premis is backwards. A warm item put into cool air doesn't draw moisture to it. A cool item introduced to warm are draws moisture. If the rifle was warmed by shooting it doesn't draw moisture from the cold air.

The only time I have seen humidity cause strange pressure is doing load development outdoors during a rain event. Seemed like the powder was drawing moisture from the air and causing high pressure signs. Since then our portable reloading room only goes out on dry days.

Steve

 

[Pdvdh]

I the condensation premis is backwards. A warm item put into cool air doesn't draw moisture to it. A cool item introduced to warm are draws moisture. If the rifle was warmed by shooting it doesn't draw moisture from the cold air.

Steve

100% correct.

There's a time/reward limit to the correcting and the associated battles, backlash, and counter sniping - even for me!

 

[McDoone]

In post 242 I proposed that this event was caused by a bad primer, either a manufacturer defect, or induced damage by the user. After reviewing all the details of his loading procedures it seems unlikely that he would have physically damaged the primer to the point that it would have failed to function normally, but there is no info about whether he handled primers with bare hands which can have the same outcome.
Where I was going with this is I believe that a primer popper/squib in a large case could cause partial ignition followed by complete detonation, the Secondary Explosion Effect mentioned by a more recent poster. (sorry, should have recognized at least your post number but failed to write it down, this is a long thread). S.S.E's have been very difficult to document but seems like powder manufacturers believe them to be credible, as they all post warnings against reduced loads of slow burning powders, and that to my knowledge was specifically the type of load that caused this to happen.
S.S.E's are reported to be catastrophic usually wrecking the gun and sometimes the user.
The mechanics of it are similar to a high compression engine. Used to be you could not go above 8.5 to 1 compression unless you used premium fuel for fear of engine wrecking detonation. Now they go well beyond that with regular gas by gradually feeding the fuel in under high pressure during ignition as the flame propagates.

I have no experience with the round in question but I have used Retumbo a fair amount and I like it. I wonder how much airspace is in the case above the powder column and if it could possibly be too much. Specifically I'm wondering if maximum loads are being reached with this bullet weight before achieving 98 percent or better case fill to prevent S.S.E. I'm picking 98 as that is my comfort zone. Basically I want a full case with a slow powder. Not sure what the actual number is but it has to be at least 95 percent. And the pressure has to be appropriate at this level of fill.

 

[Barrelnut]

Just another thing to help debunk the condensation theory. Air at -10 degrees can hold very very little moisture anyways. Cold air is extremely dry air.

 

[HARPERC]

...... There's been so much speculative banter posted in this thread that elimination of these erroneous speculative causes would greatly narrow down the list of potentially real causes.....

I think the point to thread has been the opportunity to discuss the speculative banter. The explanations provided by better engineers, and mechanics than I, to counter some of the speculation has been educational to me.

 

[5RWill]

I the condensation premis is backwards. A warm item put into cool air doesn't draw moisture to it. A cool item introduced to warm are draws moisture. If the rifle was warmed by shooting it doesn't draw moisture from the cold air.

The only time I have seen humidity cause strange pressure is doing load development outdoors during a rain event. Seemed like the powder was drawing moisture from the air and causing high pressure signs. Since then our portable reloading room only goes out on dry days.

Steve

While i don't disagree think about the chamber warming up and a cold round being inserted into it. Would that premise not hold? I had a problem with moisture in the chamber shooting suppressed in 20F even went so far as to wipe everything down to insure i wasn't picking up lube or anything. Had a tight bolt lift, pulled the case and two beads of water/liquid were on it. Do i think that's the cause of the OPs incident? Probably not.

 

[Pdvdh]

I think the point to thread has been the opportunity to discuss the speculative banter. The explanations provided by better engineers, and mechanics than I, to counter some of the speculation has been educational to me.

The primary problem with speculative banter is this: Unless somebody comes along to sort out the trash, the lay person reading the Thread is left with, well... a **** load of trash. No education in that.

Much of the membership won't remove the trash for fear of offending another member, which can lead to fussing and emotional strain and stress. Don't underestimate the value of the sanitary engineer.

But I'll give you this, there are pros and cons to most options in life.

 

[WildRose]

For the reloading of these cases Since there were so few I just hand cleaned them and whipped them off. There were no other project in progress at the time of loading and the only powder that was open was the Retumbo.

BignGreen if there is any value or it makes your assessment easier please feel free to do what you need to on the barrel. If that means cutting it open by all means do so.

Based on your analysis to date it appears that any and all pieces will be wall art and I will not be putting them back into another action.

I take personal responsibility for the outcome of my load development. I wouldn't be comfortable sending it into Remington without full disclosure that the failure resulted in part due to a hand load and that factory ammunition had not been in the rifle.

Thank you all for your continued input and analysis.

Wink, I may have missed it but did you size each case for OAL before loading? An over length case neck could very easily put a hard crimp on the bullet when chambered, hard enough to create enough of an overpressure to cause a catastrophic failure.