You don't have to worry about the issue of decreasing loads with pistol powders. There have been some instances in the past with rifle powders having secondary detonations due to small charges, but all of these have been with a small handful of very slow burning rifle powders, and noone has been able to duplicate the conditions under which this has happened. I shoot reduced rifle powder loads and use small charges of pistol powder all of the time for shooting lead bullets, as well as thousands of other people out there.