In a .50, 80 to 100 grains of powder is about all that will be usefully consumed behind a round ball. (This depends, to some extent, on how long your barrel is.) However, if firing a heavy conical, or perhaps a sabotted bullet, more powder will, up to a point, produce more velocity. Some of the fast-twist inlines are designed to be used with up to 150 grains. But, as Coondog says, the only way you will know if this is workingin your particular rifle is by shooting it with a chronograph!!

Keep yore powder dry!!