"I assume perhaps incorrectly that your mortar has a barrel length that
is maybe ten times the bore. Probably less than 2 inches. So you are
going to have to use something that burns fast. But I am a bit
skeptical of the stuff in firecrackers. It is intended to explode
with minimal containment."

Not sure about that. Stuff in firecrackers is class 2 explosive, the same as black powder. It is
called "flash powder" because of substances which make it flash into light as it burns; not burn
with any more accelerated rate than any other powder of the same granulation. An explosive that
detonates with minimal or no confinemant detonates (extremely rapid combustion) and requires
mechanical shock to start the process.

Bob Swinney



wrote in message
...
On May 21, 8:02 pm, "DoN. Nichols" wrote:
On 2010-05-21, steamer wrote:

--I've been trying for ages to get my .177 cal mortar to shoot a
pellet more than a foot. I'm using FFG which is the finest powder available
locally. What I need, I think, is the stuff that's normally packed into
firecrackers.

I'm not at all sure that I would trust that. It has a *lot*
faster burning rate than black or smokeless powders. You might as well
put a drop of nitroglycerine in it. :-)



Now' I've toyed with the idea of making a brass mortar and
pestel to grind the FFG powder into something finer but I thot I'd better
ask here B4 becoming a candidate for a Darwin Award.

I think using a brass mortar and pestle is the way to go. You can and
should ground both of them. I would stay away from ceramic is it is
usually a good insulator. And of course stay away from steel.

As already suggested -- seriously minimize the amount which you
are working with. And avoid metals in the mortar and pestle. (But for
the .177 caliber mortar, you *do* want metal, of course. :-)

How long is the barrel in the mortar? I would be tempted to use
a small pinch of Bullseye smokeless for the fast burning. But make sure
that the wall thickness is sufficient to handle the possible pressure
peaks.

Good Luck,
DoN.

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