I'm having a physics failure.
You guys are gonna think I'm a nitwit, but I can't get my head wrapped around this.
Starting charge working up a handload put the center of the group about 3.5 inches above bullseye. Increasing the charge by a grain of powder lowered the center of the group to 2 inches high.
This proceeded until the max load centered just about an inch below bullseye. All groups were fired from sandbags at 100 yards. No adjustments were made (scope, primer, seating depth - nothin'.)
I'm confused. Generally speaking, more powder should equal more velocity. Greater velocity should equal decreased bullet drop over a given (fixed) distance. Doesn't that mean the point of impact should go up instead of down?
Does this have something to do with the mass of each extra grain of powder? I have a feeling when you folks explain it I'm going to slap my forehead and say "D'oh!" but I just can't figger it on my own today.