With the velocity range you are trying to gut, 4227 is going to leave a mess behind... Not sure where you should start with Blue Dot but with Unique I use 18.0 grains with a 350 Berry's plated bullet and get 1050 fps. 20.0 gets 1225 with a Sierra or Hornady 350. This is out of a 4"...very pleasant shooting loads.

If you start with the same loads with a 300 you should be in the same velocity area...

Bob