Going that slow I use 2400 or Unique with a magnum primer in my 19s. I have seen 4227 loaded down not ignite with a standard primer. The Lee reload manual will point you in the right direction. It gives you the speed--bullet weight--and a wider powder choice for a safe load. I like 125 grain bullets but they group better out of my 19s at about 1000 fps. using a magnum case.