welcome to the dark side......... 
this is from the hodgdon pyrodex site
http://www.hodgdon.com/ml-warning.html
Pyrodex In Cartridges: The mechanics of reloading metallic cartridges are quite simple,
but there is one requirement of the modern shooter that can not be overlooked.
The modern loader must set aside his knowledge of loading with smokeless powders
and embrace the ways of years gone by. It must always be remembered that blackpowder
and Pyrodex are very inefficient powders by today’s standards. The methods
described here are consistent with good loading practices for Pyrodex and should be
followed without regard to smokeless loading practices.
Pyrodex works best in straight walled cases, but it will work satisfactorily in bottle
necked cartridges as long as our warnings are observed.
WARNING: Never allow an air space in any cartridge loaded with Pyrodex. The loading
density must be 100% by light compression. 100% loading density may be
accomplished in two ways:
The case is filled with powder to a level that will provide light compression of the
powder (1/16” to 1/8”) when the bullet is seated. Bottle necked cases must be
loaded in this manner.
In straight walled cases, filler wads may be used to reduce the powder charge. This is
done by inserting card or Polyethylene wads between the base of the bullet and the
powder. Wads should be sized to the internal diameter of the cartridge case. The
loader must be careful to insure that there are no void spaces in the assembled cartridge.
NEVER use any other type of filler material. Be careful as loads are reduced.
At some point, the bullet will fail to exit the bore.
When loading cartridges with Pyrodex it is recommended the loader use a volumetric
powder measure designed for use with black powder, or consult the manufacturer(
s) of his powder measure for their recommendations for use with black powder
substitutes.
Pyrodex does produce a corrosive residue from combustion. Even though this fouling
is softer than the fouling produced by blackpowder, firearms should be cleaned after
each use. Hodgdon Powder Co. recommends the use of natural cleaning solvents.
Cartridge cases that have been fired using Pyrodex require special care. As soon as
possible after firing, cases should be de-primed and immersed in 50% water and
white vinegar. The acidity of the vinegar will neutralize the corrosive residues remaining
in the case. Care should be taken to limit the soaking time of the cases in the
vinegar to 10 minutes. Soaking for a longer time may cause etching of the brass case
resulting in shortened case life. Rinse cases with clear water, dry and polish in a tumbler
with corncob or walnut shell media.
some load data and handling precautions also available on the goex site
http://www.goexpowder.com/index.html
