There are a lot of variables involved with the number of grains of powder in any given caliber round. Most importantly are the type of powder and the weight of the bullet. After that is the loader's preference as to the velocity of the round. For example, I load a 155 grain .40 caliber bullet using Ramshot Zip powder for a "light" velocity of about 1050 feet per second using 5.3 - 5.4 grains of powder.
Depends on the powder.
Follow the manufacturer's instructions in the owner's manual. They are not all the same.
First, find a copy of the owner's manual for YOUR pistol. Second, use ONLY black powder, or a modern black powder substitute, such as Pyrodex. The ROUGH rule of thumb is one half the bore diameter in grains of powder. A .32 cal would use ABOUT 12-16 grains of powder.
50-75 grains
40 grains of fffG
my opinion is the 45 ACP round has more knock down powder then the 40 caliber
A good place to start is with as many grains as the cal. (30 in this case)and work up from there to find the load that gives the best groupings. I shoot 35 gr. for target and 40 for hunting and 45 with a mini ball in my 32's
Most recommend is 3F powder, either true black powder or the "synthetic" or black powder substitute equivalent and between 25 and 30 grains should due nicely.
My .32 cal. mold produces pure lead round ball that weigh about 47 grains or about .107 oz.
Let's discuss some terms. GRAINS used in this context is a measure of weight. The weight will depend on WHICH powder is used, and WHICH weight bullet is used. It may vary from 4.5 grains to 12 grains. For your own safety, NO ONE should ask for load data from an open site such as Wikianswers. For all you can tell, I am 11 years old, and Mom does not know I am on the computer. (I'm not, and she knows) PLEASE obtain load data from the powder and bullet maker sites- trusted data.
Contact the maker of your rifle for their instructions. It will depend on bullet weight. Assuming you mean a .50 cal MUZZLELOADER- and not a .50 Barrett- between 75 and 90 grains of ffG black powder is an average load for a patched ball.
120 grains max. Any more than that wouldn't be good.