The S.E.E. Phenomenon, smokeless in blackpowder guns

[Bobby Ironsights]

Hi.

I'm too fond of the blackpowder stench to use anything else in my guns, but I came across something that might interest all you experimenters out there.

I've been researching subsonic (low velocity) loads for my other guns and come across a phenomenon that is both interesting and somewhat scary.

I'd assumed, like many others naturally would, that a very small powder charge could never be dangerous.

Turns out I was wrong.

There is something called the secondary explosive effect. It happens when the charge is so small, that the heat and pressures created are too low to completely burn the smokeless powder.

Tars and resins and these incomplete combustion byproducts build up in the chamber and bore.

And sooner or later, enough can (in rare cases) build up enough to detonate and blow the firearm to pieces.

It's not that unusual, I guess, chimney fires all over the country happen just like that. Wood resins and tars aren't nitrated though eh?

The literature I read said to always use magnum primers that burn hotter than normal to ensure more complete combustion, check the bore regularly when shooting strings, by running a clean patch down there from time to time. It also said to watch out for hangfires, or alot of smoke coming out of the barrel or a small flame burning on the tip of the bore, unusually powerful shots, in a string of identical cartriges.

Well, it occured to me, that if this was a problem with subsonic loads, it might be of interest to shooters who use smokeless, loaded light; in blackpowder arms.

Bobby

 

[Win 38-55]

Whether this actually occurs or not, I'm not sure. Once the bullet is proceeding down the bore, the effective case capacity becomes so large, that I just don't see how the pressure could be of concern, even if SEE occurs. As for me, I don't like a case that is too empty. My preference with smokeless powders in black powder cases, is a capacity load, very slightly compressed. That requires experimenting a bit to find the right speed powder that will do that.

 

[senior]

Tars and resins and these incomplete combustion byproducts build up in the chamber and bore.

They must be talking about muzzle loaders, the next bullet out of a gun will clean the bore of unburned powder or residue! & the next charge in an uncleaned case would certainly ignite unburned residue.

I prefer to stuff my smokeless loads with toilet paper to fill the case & keep that little powder charge from moving around. You might want to beware of fire if firing those loads in the bush but I rarly shoot those old gun anyplace other than my range.

 

[mooncoon]

I think SEE are extremely rare and occur with slow burning smokeless powders combined with very light loads that only partially fill the case. I also think they are caused possibly by the primer blowing the powder into a suspension before the bullet leaves the case and this suspension then burning at a much higher rate than would be the case for a full charge. I seem to recall the Brownell in his book on firearm pressure factors tried unsuccessfully to recreate a SEE and that in general their true cause remains quite speculative and more or less non reproducible. I believe they do exist but so rare that their true cause remains unknown.

cheers mooncoon

 

[Sharps '63]

Smokeless in BPCRs

Bobby

I shoot 3031, Varget and XMP5744 in my 45-70s and 50-70. I believe that SR4759 also serves well in large capacity cases. I've managed to find a load with XMP4744 that shoots into the same group as BP with my 50-70 at 50 and 100 yards.

You get good load density and I don't use wads or fillers. I've tried Trail Boss and find it useless in 45-70 but love it in 45 LC.

However, BPCRs ought to shot with the holy black and that is what I do in the main. Smokeless is for when I don't want the brass cleaning chore afterwards.

The detonation thing used to be a hot topic amongst bullseye shooters with powder puff loads in .38 Spl. Easy to avoid - don't do it!

 

[fat tony]

This was discussed at the Finnish site gunwriters on the web, I don't remember all of it but they suggested you stay clear of attempting to make subsonic loads for the .243 Winchester, why, I can't say.