I was talking to Richard a while back and he made mention that his 80, 85 90 grn bullets all were the same jackets ,same length , just have more lead in the core. My question is does this change bc and required twist in these different weights.
I thought that the bc would change with weight in the same jacket.
I believe you're right!
ballistic coefficient: BC=SD/i
where: BC is the ballistic coefficient, SD is the sectional density of the bullet, and i is the form factor of the bullet.
I found this at Dan Lilja's website.
If "i" changes not, it retains its form or shape , then the higher the weight the higher the "SD" would be and the higher the BC.
JWP475 is right on the money about the twist rate needed would be the same but not the BC.
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Normaly you are correct,but the original post stated that the 3 bullets were the same lenght,therefore if the shape is the same then the BC will be identical and only the SD will change........... Normaly a heavier bullet is longer therfore both the SD and BC will increase....BC is a numerical value of a bullets areodinamoc shape and is some what tied to wieght,but not totaly....Other wise all bullets of the same wieght would have the same bc if the shape were the same and this is not the case.... A mono metal bullet(copper) of the same wieght and same shape will have a higher BC than a lead core bullet because it will be longer... A tungstan core bullet of the same wieght as a Lead core bullet and a monometal (copper) will have the lower BC because it will be shorter... 3 different wieght lead core bullets with the same lenght and shape will have the same BC............
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