Black powder turkey loads
 

I'm fixin to load up some test rounds for my 1885 0 grade 10 gauge and was wondering what would be the lightest I should go for turkeys? I'm using #6 shot and plan to start my loading at 3 1/4 dram of ffg and 1 3/8 oz of shot.

I would use 7 1/2 and go for a head shot. You'd have more shot and the 7 1/2s will do the job. Your powder to shot ratio is on the money. Maybe load up some 6 and 7.5 shot shells and see what patterns better, every gun is different. My wifes 28ga wouldn't pattern 8.5 shot worth a darn.