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. :-)

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.


* * * * * * * 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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