Let me get this right... you fired all shots at the same target? Ummm no.
You need to shoot 3 or 4 groups (3, 4 or 5 shots each) of each load at different targets. That means 10-20 rounds for each load. If you work up 10 loads at home you're gonna need 30-40 different targets.
BTW, for initial testin loading at 1gr increments is more than good enough. Most testing is done a 100 yards.