Asked about detonation folks

I was asked about detonation so here goes a try at explaining it;
conventional cartridge powder burn example:
picture the powder compressed burning in the case from the primer end forward slowly building up pressure and pushing the unburnt powder out behind the boolit. as the boolit and powder continue to traverse the bbl, more powder continues to ignite to create higher pressure on a gradual scale till the boolit exits the muzzle.

reduced load example:
when the powder doesn't fill the case you get air space, for example, picture a half filled case, the powder has a lot of surface area for the primer flash to ignite all at once instead of the chain reaction as in a full case. this all at once ignition creates rude pressure spikes and in some cases, KABOOM.

To help with this issue, people will fill the rest of the case with polyfill, or cornmeal, to keep the powder column on top of the primer. this adds another variable to the mix of reloading components seeing as you have to weigh the polyfill/cornmeal to be sure of consistency, but it's worth it for those of us that use mild loads to get the older guns out of the closet and or boolit loads for milsurps

It's advisable to stay in the prescribed ladders of reloading data for this reason, too little powder creates inconsistencies and dangerous pressure spikes as well as too much powder. i've read many an article of kabooms happening in cases of both sqib and double throws.

to combat this from a commercial direction, Trail boss was created and works great. it's a powder with extremely light density so it takes up lots of space. google forums and research it if you like the reduced loads idea. it seems to be the safest alternative that I can see. accurate too.

XbonesX and other folks on here are a lot better than I at finding previous threads and youtube vids to support this. let alone full of knowledge themselves so I'll let them chime in.

Cheers

WOW! Great explanation

I've been meaning to get some trailboss...I think you talked me into it.

the first time I bought trail boss was pretty funny...

I asked the local shop if they had any and he pointed to the tub of it on the shelf, so I asked how much, he said 9.99 plus tax, I was so excited, instantly forked over the dough and ran home to work up a load... then noticed it was only half a pound LOL same size tub that the other powders come in 1 pound quantities so it works out about the same price wise, but still pretty funny. it's around 12bucks for a 9oz can now

Hello CMAsailor,
Please take this as friendly. But there must be more to the story. All 38 special loads call for a very small about of Bullseye or some other fast-burning powder. The powder companies and others that publish recipes for 38 special would not publish such data if it were dangerous. What I had heard is that this phenomenon only applies to slow burning powders like Winchester 296.

EdgarEg wrote:Hello CMAsailor,
Please take this as friendly. But there must be more to the story. All 38 special loads call for a very small about of Bullseye or some other fast-burning powder. The powder companies and others that publish recipes for 38 special would not publish such data if it were dangerous. What I had heard is that this phenomenon only applies to slow burning powders like Winchester 296.

That would be correct. Common sense would tell most that fast burning powders really can't be reduced. Reduced loads are usually for slower burning magnum powders or rifle powders as you mentioned and are only used in large pistol or rifle cases.

This seems to be saying that even fast burning powders have the danger of detonation.

http://www.vihtavuori-lapua.com/pdfs/cowboy.pdf

It says:
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3) Risk for underload detonation

This risk is always present when using highly reduced loads of any smokeless powder. The large free space in the case may generate a pressure wave which can cause, in the worst case, powder to burn as a shock wave, i.e. to detonate, instead of normal fast burning process. The extremely sharp pressure peeks involved in detonation can destroy the weapon and may lead to serious injury.

All these loads given here are extensively pressure tested and no sings [sic] of underload detonation were found. We strongly recommend everyone to follow strictly these tables to minimize the risk for underload detonation
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I have been reading some on this subject of detonation. I do not yet feel that I understand it.