As promised, here's what I'm thinking about SEE.
Big bangs are reported with small charges of slow burning powders, sometimes blowing up the gun.
This happens infrequently and appears to be non-reproducible and is explained in great detail by theorists. (Some similarities to the chamber-ringing phenomenon.)
I'm starting to have enough powder measure bridging events documented to see that it is entirely possible to drop too much powder in one case out of a lot of many. 
(Please, check your charged cases with a flashlight!)
So, I'm beginning to suspect that this small-charge phenomenon may be really a large-charge phenomenon caused by powder bridging in the measure.
I'm sure that opinions abound, has anyone any evidence to counter this theory/explanation?
joe b.

What MB said, and plenty of it, Joe

Good morning, Joe;

I have followed this SEE thing ever since it started being reported.  What you say about not being able to reproduce it was at one time true.  Several years ago, I read the ONLY explanation that has ever made sense to me and I will explain the mechanism here.

I regret that I did not save the paper this was explained in, but I didn't.  So believe it or not.  The report was from a responsible ballistics lab.

The original reproduceable observation was not with reduced charges, but with normal charges in a well worn Italian Carcano rifle.  The throat was long and rough.  When it was fired, the bullet moved through the long throat on primer power and maybe a little powder burn.  It then stopped and was "wedged" into the throat to provide a very heavy resistance when the powder charge began to burn vigorously.

Flavorless powder (the white stuff) burning rate depends largely on the pressure within which it burns.  As it burns, it produces pressure and then the powder burns faster.  As it burns faster, it produces more pressure.  As it produces more pressure, it burns faster and so on..... ad infinitum.... ad nauseum.

In the case above, the bullet itself is moved so early in the burn that it becomes an obstruction when the powder starts to burn "normally" and pressure spikes.  Note that with faster powder, the bullet would not have an opportunity to move and stop.

In the case of small charges in large cases, the same conditions would apply.  The primer and probably the first powder burn pushes the bullet into the rifling where it sticks and becomes an obstruction as pressure begins to rise.

Usually the best results with real powder (black) are found with a heavy bullet and a crimp or with the bullet seated into the rifling.  The purpose is to keep the bullet from moving until there is enough pressure to move it in one swift smooth movement.  This one movement is much easier to accomplish than what the lab that published these results called "slip stick".

I don't tell anyone what to believe, but I (italicize) believe that this is a good observation by a responsible lab.  Much more importantly, it fits into the pattern of other known phenomena including the idea of chamber ringing.

Y'all be good.

horsefly

Quote:



IMO anyone who hasn't read and reread both of Ackley's books cannot be said to be truly informed on their various subjects, e.g. the SEE phenomenon and several other sorts of action blowups among others. IMO they are truly seminal works. Certainly not the last word but rather in many cases the first word on many particular subjects.
JMO, Joe