Home Forums Hunting & Shooting Hunter's Campfire model 70 explosion

I guess ol miles58 can’t see the mangled ph ucking bullet still stuffed inside the dented case..

I have bought lots of guns to overload them.


All I ever see with bolt actions is the bolt lugs bend, the bolt lug abutments in the receiver dent, the case head fails, pieces of the bolt head break off, and the extractor blows out the back in pieces along with pieces of the case head.

In the OP picture, the bolt lugs seem to have plowed right through the lug abutments in the receiver.

I have not seen anything like that in my failures. I see the abutments as slightly deforming in my failures. [bend, but not break]

Smokeless powders are low-order explosives
that burn [conflagrate]. Not detonate.
where under certain conditions (containment in
brass case/rifle chamber) you get an explosion.

You can also ignite/burn C4 without achieving
detonation..It requires a certain level of shock
to alter the chemical bond (for detonation).

I have only seen a couple of mode 70s blown up. Both I think happened to be 7 mags IIRC.
l
To produce a symmetrical dent like that without cuts/scratches indicates either very high and very localized pressure hydraulic most probably or possibly gas pressure. Producing that dent without being larger, without deflection in one direction or another, without cutting through would seem highly unlikely in a situation in which the case is not well enclosed all the way around and extending above and below the dent. Applying that kind of pressure to an unenclosed and unsupported case would have to deform the case pretty obviously in other ways and places. I suppose that a steel BB fired at high enough velocity at a perfect angle to the shoulder and with the case free to move some feet as a result could produce that dent without other obvious damage.

Is it possible that the damage (dent) occurred when the rifle exploded?

That would seem to require the presence of additional damage to the brass and it would seem to require additional evidence of powder/brass from the chamber round on it. If I had to guess, my guess would be that the round was not in the magazine and was likely on the bench with the first fired round and that the discoloration on the bullet could well be blood which from the description of the wounds was apparently available on site.

All I am saying is that the shoulder dent is evidence that that round may have been a reload and I believe it was. That evidence alone is enough reason to be careful about having that round and the remaining rounds in the box it supposedly came from examined. Both of the model 70s I saw that were blown up were reloads. I do not know now and never really did know then what the load was, or that it was in fact a bad load. It seems to me that basic common sense says to eliminate a bad load first and doubly so when there is evidence like this of a reload. That out of the way, then metallurgy work might tell you something, but the degree of certainty is not likely to be real high. I spent 3 years doing metallurgy on something that was previously diagnosed wrong and in a product whose proper function was every bit as critical to the user's health. I believe that if there is a bullet lodged in the barrel (reasonable chance but I have seen a 270 that digested a .308 bullet) and if the round on the table and those in the box are examined an answer will turn up that makes sense.

Rather than yield with deformity, the bottom lug abutment broke.

I usually see equal damage to bolt lug and lug abutment, but in this case only the abutment seemed to fail.

This would suggest to me that the receiver was brittle.

Maybe the smith read the Kuhnhausen book on Mausers and wanted heat treat.

Maybe the smith had trouble getting it to feed and ground on the feed ramp
I would bet that the initial problem was soft brass failing, and old model 70s just can’t handle escaping gas well

Looks like the lower bolt lug got shortened and bent, while the upper lug is intact.

That means the receiver split [and moved the upper lug abutment] before the bolt moved back.

Which means that, even if the smith compromised the lower abutment with feed ramp mods, the top abutment was still first to fail.

The barrel isn’t split or damaged that I can see. If this was a severe over pressure that exploded the action the barrel would have split also. The action is the only thing that failed and it’s almost certain that it was from a brittle and cracked lug abutment. I personally had a M70 detonate like this action but it was from using the wrong powder. Both the barrel and the action split because the failure was from pressure that exceeded the strength of barrel and action. In this case just the action failed and I believe it had simply become weak and the lug abutments had probably already been set back and developed cracks. It reached its failure point on this final shot.

Still of the opinion that overtightening of a non-factory, replacement barrel cracked the receiver.

I’m sure everyone here has reloaded more than me, but all of the lube dents I’ve ever seen or produced, were above the base of the shoulder, never on it or below it.

I have worked on a Ruger in 7mm mag.that had a 270 win.shot in it.

It broke the stock in two at the wrist and the floor plate had a pronounced bow to it.

The fellow that shot it only had a few small cuts from brass.

This happened shooting at a coyote while sitting his truck.

Bet the sound was epic.

And that dent was not made with to much lube.

Lube dents occur above, below, on the shoulder, into the neck and even in straight wall cases. The common defining characteristics are that it is a smooth (no sharp crease) dent with the rest of the case unmarked because it was supported tightly by the sizing die and pronounced length aligned with the length of the case.. Sometimes they are deeper at one end than the other. Most of the time they are symmetrical side to side but not predictably so end to end. I do not think I have ever seen a case that had multiple lube dents, but I suppose someone discovering their first one might lube it up again and run the case through the sizer trying to fix it and create a second dent.

From:

https://saami.wpengine.com/wp-conte...nd-Brochure-Master-Revised-8-24-2020.pdf


Bruce

This is a common misconception. A severe over-pressure will not always split the barrel. In the example below the shooter filled the .257 Weatherby case with BlueDot and fired. One can clearly see that the barrel was not split. The rifle was a Weatherby Vanguard...


https://thefiringline.com/forums/showthread.php?t=341348&highlight=blue+dot



.

That's an excellent list of what can fit into a chamber and may fire.

How would one close the bolt on a 7mm ultra
or 300win cartridge?

A little side track to the topic here, but I got interested in pressure events long ago with cast bullets and light charges and case fillers etc so this tragic event re awakened my interest. My google fu is pretty poor, my library limited, but I tried again to research air space and slow powders...it's shocking that anything that dangerous can be that hard to find data on. Anecdotally, I had a friend, now deceased who was involved in a tort case in which he, as an expert witness, duplicated a light load of slow powder in a .264 Win I think...with some input by Rick Jamison, blew a model 70 all to hell and documented and filmed the whole thing. After all that, a settlement was reached, all the plaintiff got was medical expenses and an undisclosed sum, the ammo company (I can't recall) admitting no liability. Anyway, first try, John blew up the model 70 with a light charge.

😀😀😀😀😀

BINGO!! New year, same old dickhead58.

I’ve seen one modern 308 M70 (FN) which literally blew the f up.

An acquaintance who had recently started reloading used an appropriate powder charge by weight, but he accidentally swapped whatever IMR powder he had on the bench for his .40, instead of IMR 4064.

Barrel landed at the 50 yard line, left side of action peeled out like a banana, stock cracked right at the front of action, scope rail and scope bent. Bolt still in battery. Got a pic, don’t really know how to post it these days.

Other than [bleep] his pants, luckily the shooter was unharmed.

Anyone else have more info on this, or possibly some documentation? I've been considering the SEE theory along with a few others....