From Cartridges of the World 2nd ed
It was invented in 1881 by H&H. In the 1883 field trials using open sights 10 shots grouped 1 1/2" at 50 yards.
Original loading
300 (.295) Rook
1 1/8" OAL
Bullet 80grs (Lead)
Powder 4 1/2grs of CN (Cadet neonite)
MV 1100 ME 915 Vel@100 yards 215 Energy @ 100 yards 150 drop 16.5"
Recommended loadings from the above:
Bullet 90grs powder 4759 6grs MV 1150 ME 245 lyman #311245
Bullet 90grs powder Unique 5grs MV 1100 ME 218
Bullet 80grs Black 10,FL MV 1100 ME 215
He compares it the 32 Extra Long
Bertram makes brass for the 300. Buffalo Arms or MidwayUSA have it.
For cast bullets look at the Laser Cast 78grs:
http://www.laser-cast.com/32Cal.htmlPete