I'm new to BP cartridge loading for a 45/70 using RCBS 500 grain BPS bullets in Starline cases. Using .10 to .15 inch compression, I can get 57 grains of FFg in the case with a .125 inch grease cookie (SPG) plus a .030 veggie wad under the bullet. This give me a COL of 2.860 inches with finger seating. The bullet's top grease groove is exposed. This is about the maximum COL I can chamber in my Pedersoli.
Are there any guidelines or recommendations for how much compression I should use? My BP rifle range goes to 500 yards so this will be my maximum distance. I know I can get more powder in the case with the 405 grain bullet but the 500 bullet appealed to me. What are your thoughts and experiences? Thank you.