You bet. My Speer Manual #14 doesn't list "minimum" and "maximum" powder charges for shotshell capsules however. It just lists one recommend charge for the type of powder.
Anyway, for the .45 Colt Shot shotshell capsule my manual lists 7.5 grains of Unique for 975fps, or 5.5 grains of Bullseye for 875fps. Both loads were tested in a 6" Model 25-5 Smith.
That does it. I hike around in the National Grasslands in southern Colorado a lot. Once in a while a rattlesanke tries to convince me that the trail is his--and wins. Next time I'll be prepared and argue with him.
Hey Sturgell, I have seen Mike Venturino do that same thing with 45 Colt. Mike used gas checks for his wads.
In his tests the lower powder charges seemed to pattern a lot better.
I wonder if your data taken from the Speer shot capsules is a touch warm because your wads are pressed down over the powder... with the shot capsules there is a lot of room and they aren't seated as deep.
I know seating depth can raise pressures quite a bit. Something to experiment with...