300 RUM Kaboom

John Y Cannuck

John Y Cannuck

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Over at AR
2.1.jpg


More pics page two of the thread

http://forums.accuratereloading.com/groupee/forums/a/tpc/f/2511043/m/810104443
 
I read what was on AR's page, and I concur with some of the opions there - this was not a minor mistake like the case being a bit long or a slight over load. This was a big league screw up - say like loading a .338 bullet in a .300 Ultra case.
 
My guess is that a combo of things went wrong together to cause that KB. Maybe the wrong powder/amount was put in? Maybe the 'jammed' case caused pressures to spike? Maybe the receiver had been fatigued from extreme pressures and simply couldn't take that final firing?

For an action to KB, I would expect pressures to exceed 150000PSI, probably more like 200,000PSI (no one seems to want to release that type of info). Proof loads are usually around 120000PSI and don't blow up actions. That's twice what a magnum load should be so there is little risk of a KB from a just over max load (not suggesting you load that way mind you). Alot of other things 'fails' before you get that toasty. Primers usually show the first signs of trouble but are not definitive.

As someone said, the moons and planets all lined up and bad things happened.

Glad to no one got seriously hurt.

Jerry

PS I wonder what diameter the barrel thread was? 1.060" or the larger one?
 
From the bits I have read, the barrel is OK, there is nothing in the bore right now (bullet left during the KB), the action is split cleanly down the middle, no feedback on what the bolt looks like (lugs sheared or bolt bent), the case is still in the barrel but the rear is blown off, the amount of powder is over all listed data but only by a grain or two, maybe three, a 308 bullet was loaded (big question mark) Did I miss anything?

I can never verify this and pure speculation but I would consider this an action failure, if a 308 bullet was used. The barrel handled the pressure which also vented with the bullet leaving the bore. The pressure was high but high enough? I have seen destruction tests where bullets were jammed into the barrel so they would not come out then a cartridge fired with less destruction. Actions did not grenade!

The bolt probably still has both lugs and no visible sign of damage (my bet) except dings from being launched and hitting people/stuff. The case separation was due to the bolt's rapid increase in headspace. The case was tough to chamber, not sloppy or loose. Case separation usually doesn't occur if the case has no where to go. Primer pocket failure is where it would vent.

I wonder...

Jerry
 
mysticplayer said:
I have seen destruction tests where bullets were jammed into the barrel so they would not come out then a cartridge fired with less destruction. Actions did not grenade!
Click to expand...

I have read of similar tests, and the actions might stretch or incur lug setback, but not come apart.

One thing we do know, it was not headspace if it was hard to chamber. Clearly, the bolt face had to be hard against the case.

Ted
 
That action was a small shank barreled action and therefore thicker, I can tell by the pic. The action normally does not take pressure, the chamber and brass does. When the case head separated due to overpressure, the gas flow was redirected out the notch in the boltface and out the vent hole on right side of the action. One side vents gas depending on wether if its right or left handed action from the boltface notch [which isn't directly lined up to the vent hole] and the other side for the firing pin hole which is directly lined up with the vent hole. The baffle stops the gas from flowing back further into the action. Problem was, too much pressure too fast and the very large inner diameter of the action was under way too much pressure for it to handle. The action turned into a chamber and if a Savage action couldn't take it, it isn't likely any other could either.

It could have been the liquidified brass plugging the vent hole that caused the action to let go. That's my guess.
 
mysticplayer said:
My guess is that a combo of things went wrong together to cause that KB. Maybe the wrong powder/amount was put in? Maybe the 'jammed' case caused pressures to spike? Maybe the receiver had been fatigued from extreme pressures and simply couldn't take that final firing?

For an action to KB, I would expect pressures to exceed 150000PSI, probably more like 200,000PSI (no one seems to want to release that type of info). Proof loads are usually around 120000PSI and don't blow up actions. That's twice what a magnum load should be so there is little risk of a KB from a just over max load (not suggesting you load that way mind you). Alot of other things 'fails' before you get that toasty. Primers usually show the first signs of trouble but are not definitive.

As someone said, the moons and planets all lined up and bad things happened.

Glad to no one got seriously hurt.

Jerry

PS I wonder what diameter the barrel thread was? 1.060" or the larger one?
Click to expand...

The tensile strength of a brass case is about 80,000 PSI, what do they use to proof the barrel, kryptonite? :wink:
 
for sale: one Savage 300RUM very good condition. Synthetic stock has a small handling scratch on the side. Action is still really tight. Only has a few rounds through it.

joking aside, good to hear the shooters were not badly injured or mamed for life.
 
Hitzy, the tensile strength (destruction) of the brass CHAMBERED case is determined by the next metal part to fail or the amount of space the case can grow.

Now that tensile strength may also illustrate its elastic limits. That makes sense to indicate why brass 'grows' during firing. Brass can't spring back.

If brass while chambered was able to 'explode' at 85,000PSI, I bet ALOT of shooters would no longer be with us.
Jerry
 
IMHO, this case was ALL reloader error. The guy admitted his loads were over spec by a few grains. Now couple that with a stupid mistake like a charge thrown higher than he thought or worse het, maybe he loaded it full of H4227 or something and didn't notice?

Fact is, buddy would likely be too embarassed to tel the truth is it was bone-headedness that caused this. And frankly, the bolt should NOT have been hard to close.

Maybe the case was on the verge of head separation and he was neck sizing - who knows? This could explain the rough chambering if the base was already bulged.

Couple that with assholish overpower loads by an ignorant loader, or possibly a faulty powder measure threw a huge charge (doubtful), or maybe the wrong powder and GI Joe the hot-loading 300RUM superhero brushes once again with a chance to win the Darwin award :roll:
 
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