Just for comparision as I do not have a Gov. I dug through my old chrongraph data and From a 4" SW Mt Gun 625 -dash infinity.
With a hand cast (from a old forum member) 240 gr LSWC and 9.3 grains of Unique I got an avg of 915 FPS, ES-36 and SD of 14.
That load is about max for me and that gun. I think a lot has to do with a heavy roll crimp that can be put on lead vs plated so the powder has a chance to burn completly and build pressure.
Even if you use
some theory of 50- fps per inch (not sure if that is valid)then you in t should get around 800 fps.
Here you can put loads side by side.
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BBTI - Ballistics by the Inch :: .45 Colt Results