I don't have my guide gun any more, but looking through my notes ...
52gr of 3031 has produce tight groups for me, that's about 1800 fps.
50gr of 4895 will get you your 1600 fps.
About all I shoot any more is Trail Boss. 12.5 gr is right at 1000 fps and makes for a pleasant afternoon of shooting.
My cowboy tends to run a 200 fps more than the Guide Gun.
