"Terry Coombs" fired this volley in news:mknpap$594$1
@dont-email.me:

They're also supposed to work really well to ball mill homemade black
powder .

Not even close, Terry. The minimum 'correct' load for media to properly
ball mill (anything) is 50% full, with 25% of the empty volume in
material to be ground.

Typically, amateur BP-makers use hardened lead media -- about 1/2" in
diamter for that particular 'tumbler'. When filled with 5lb of that
lead, the thing will hardly turn over, much less turn at the optimum
speed (about 90rpm) for that 4-7/8" i.d. jar.

It requires re-work of the support bearings AND the motor's being
replaced in order to mill continually at the proper speed.

Some of those folks who report that "it works fine" are also reporting
milling times as long as 24 hours. At the proper speed and charging
factors, it will produce better-than-commercial BP in 2-1/2 to 4 hours.

Lloyd (who wrote the book on it "Ball Milling Theory and Practice for the
Amateur Pyrotechnician")