I have the 26 inch barrel 243 and a 22 inch that collects dust. I don't believe the 22 or less inch can effectively shoot 100 and above with the super slow powders.
I've chronoed R-25 and R-26 100, 105, 107's to get right on the 3100 fps mark and then went to work on seating depth etc to dial them in. One of the best additional items I found for accuracy was the RCBS case trimmer. I bought the inside/outside neck turning attachments to center the bullet to the bore. I've play with case throat length and diameter. I've also got into converting 308 Lake city brass into 243. Much thicker brass which looses up to 3 or so grains of powder compared to a 243 win case. Much thicker and more efficient.. I clean in a wet tumbler with stainless steel rod shot, resize to 260 rem without the expander ball and then on to my foster Pres. dies. I trim to right at the Saami max length spec. I feel that it has more hold on the loaded bullet. Then I do the turning to where the loaded bullet case has 2-3 thou. chamber clearance.
Over the years I've tried them all R-22, 7828, h1000, magPro. One of the powders that has promise in the 87 - 100 gr. is Superformance loading started right in the H4831 data
http://rcbs.com/Products/Case-Preparation/Case-Trimming/Universal-Case-Prep-Center.aspx
I've chronoed R-25 and R-26 100, 105, 107's to get right on the 3100 fps mark and then went to work on seating depth etc to dial them in. One of the best additional items I found for accuracy was the RCBS case trimmer. I bought the inside/outside neck turning attachments to center the bullet to the bore. I've play with case throat length and diameter. I've also got into converting 308 Lake city brass into 243. Much thicker brass which looses up to 3 or so grains of powder compared to a 243 win case. Much thicker and more efficient.. I clean in a wet tumbler with stainless steel rod shot, resize to 260 rem without the expander ball and then on to my foster Pres. dies. I trim to right at the Saami max length spec. I feel that it has more hold on the loaded bullet. Then I do the turning to where the loaded bullet case has 2-3 thou. chamber clearance.
Over the years I've tried them all R-22, 7828, h1000, magPro. One of the powders that has promise in the 87 - 100 gr. is Superformance loading started right in the H4831 data
http://rcbs.com/Products/Case-Preparation/Case-Trimming/Universal-Case-Prep-Center.aspx