Mike,
Hornady made a pistol powder measure that used/made the powder bushing you are talking about, it is 1/2 inch tall, I don't think they make the bushing any more. I have their 1986 catalog with a powder chart, PM me a email address and I will send you a picture of it. It shows #5 bushing to be 3.7 grains of bullseye. Bruce in NJ who owns Star makes the bushings.
Tom