at M.D's advice I tried 4166 4451 and 4955. 4166 is my go to powder now for 80 grain barnes out of the 257 Roberts and 110 barnes out of the 7-08. I'll check my notes but I'm pretty sure 4166 worked well with my 30-30 and 223 also. I would think your 243 with the bullet weights you want to run, would be a great candidate for 4166.
