Was discussing this with a friend over the weekend. Has anyone scientifically documented that this has happened rather than just by deduction and "assume" that that is what happened when they see excess pressure signs with what should have been mild loads. It should be possible to see it on the pressure trace shold it not? Or is the whole SSE thing a myth?

Regards,
JohnT

No it happened last night after 10 Burritos and a half doz. bottles of Alaskan Amber!!!!

It's not a myth.

It happens.

I can produce it at will but don't since I'm not "into" blowing guns up.

There are more than one way to get the result, which I long ago resolved not to write about, because as sure as shootin', some nitwit would blow some fingers off just trying to prove me wrong. I frequently warn about these unwise loading practices, of course, but I don't present them as causes of the "SEE" or mention them in discussions of the "SEE."

The simplest way to put it is that you don't have to worry about the "SEE" if
(a) you don't try to wring the last possible foot/second of muzzle velocity out of your gun
and
(b) you always use ninety to a hundred percent of a case-filling charge of your optimum powder (which may not be your personal favorite and may not be listed in your manual).

Seems like Dr. Howell wrote an article about it in RifleShooter mag several years ago...I see if I can dig it up.


OK, April 1998...page 70. If you can find a copy it will cover a lot without him having to type it all again.

I seem to recall that most of the SEE blowups (and to the OP, no there wern't signs of excess pressure) were from working down "mouse fart" loads, not trying to gain a few extra FPS.
This "sample" is hanging on my gunsmiths wall, the load data presented is what he remembers (it's been more than a few years) loading it with. 9 rounds fired, 9 holes in the target, rifle blew on shot # 10.

True about working up "mouse" loads. But P. T. Kekkonen wrote of S.E.E. occurring in a .243 WCF, 80 grain bullet, and a reduced charge of then new Norma MRP. He wrote that the pressure test setup blew up - "disintegrated" - and the test was repeated. The second testing setup blew up after a few shots (pressures slightly less than normal) with the piezo gauge peaking out at its maximum, about 150,000 PSI, before breaking. He opined that the actual peak pressure could have exceeded ten times that.

THE POWDER CHARGE WAS ONLY 15 PERCENT BELOW MAXIMUM, MAXIMUM BEING A COMPRESSED LOAD!

The lesson I drew is that if you go below tested starting loads you MAY be getting into S.E.E. territory, particularly with slow powders.

Source:

I`ve always been under the assumption S.E.E was a product of light charges of slow powder along with light for caliber bullets. Tailgunners example of a 45/70, 500 gr bullet with 3031 shoots that all to......
3031 is a middle of the road 45/70 powder though, as far as burn rates go.
Tailgunner how did the guy pulling the trigger fair? The rifle "looks" painful!

Greenhouse Gases, eh?

BMT

FWIW:

Light loads that are safe to use are listed by Hodgdon as "youth" loads.

Freely available information.

No need to go blowing things up to make up loads.

BMT

I'm no engineer, and when By Smalley (rocket engineer and cartridge designer) tried to explain Secondary Explosion Effect to me, I simply got lost in the explanation. I'm certain that I can't even begin to reproduce his words, but the SEE phenomenon has something to do with reflected wave fronts, harmonic amplification and localized powder heating. I think. The true SEE requires slow powders coupled with a certain amount of airspace and also depends on case shape, IIRC.

Other "blowups" can happen, but are not caused by a true SEE, the cause usually being double or excessive powder charge. The classic blowup is the .38 Special target load of 2.7 Bullseye under a deep-seated wadcutter, except that the burst load probably contained a 5.4 Bullseye double charge.