group movement?

[art sehnke]

Help!!! I have been shooting .44 cal.(.430 dia.),240 grn. XTP's in a Harvester green Crush Rib sabot over 80 grns. of BH209 and getting good groups very near the bullseye, my point of aim. Last night I increased the load to 90 grns. & the center of the group leaped upward almost 4". The first shot was nearly off the target @almost 6" high!!!
I am using an old Bushnell fixed 4X scope.

I also tried some .300 gr. XTP's with the same increase
, going from decent groups @ 80 grs. BH209 to a 4" grouping using the 90 grain load & it also moved quite a bit upward on the target.

Is it to be expected to move that far up the target making a 10 grains increase in the load???? I made a 12 click DOWN adjustment to my scope and that brought the center of the 4 shot group down to about 2.5" above the bull& 1" left windage. I just didn't expect that much of a change in a 10 grain increase. Any thoughts welcome. Thank you.
Art

 

[Anonymous]

I'd try another scope, and see what happens. No,,,I wouldn't expect that much variance in a 10gr. change.

 

[Underclocked]

Go to 100 and see what happens. Have you tweaked any stock or scope screws?