There will be variation in this formula based on how high your line of sight on the rifle is above the line of light at the bore. So, scope versus iron sights make a difference. Bullet velocity makes a difference, thus barrel length in addition to load is a factor. You just have to do the work. You cannot sight in at 25 yards and predict your 100 yard performance.
My preference is to sight in at 50 yards and hold off for 25 and 100 yards, but that is for round ball muzzleloaders. Your results will vary ;-)

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Kind regards, Heinz