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.
Wildcat bullets
- Thread starter hogslayer
- Start date
Cheyenne19
Well-Known Member
I thought that the bc would change with weight in the same jacket.
Eaglet
Well-Known Member
I believe you're right!
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.
jwp475
Well-Known Member
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............
Jon A
Well-Known Member
No, the BC's will change. Identical shape, identical amount of aerodynamic drag but still a different BC.
BC is not drag. BC is the effect of that drag on the bullet. The same amount of drag slows the light bullet down faster, meaning the light bullet will have a lower BC even with the same drag on it.
BC is not drag. BC is the effect of that drag on the bullet. The same amount of drag slows the light bullet down faster, meaning the light bullet will have a lower BC even with the same drag on it.
jwp475
Well-Known Member
Explain how the 265 grain 338 Aluminum tipped Wildcat bullets have a higher BC than the 300 SMK..Shawn Carlock shot some and had to plug in a .9 BC to match his drops...
Below is a 265 grain Aluminum Tipped Wildcat compaired to a 300 grain SMK and a solid copper 300 grain bullet
Below is a 265 grain Aluminum Tipped Wildcat compaired to a 300 grain SMK and a solid copper 300 grain bullet
steve smith
Well-Known Member
To Quote Jon A
"Identical shape, identical amount of aerodynamic drag but still a different BC."
The two bullets jwp475 mentioned do if fact have dissimilar shapes. Even though the WC bullet is lighter it is also more aerodynamic. Thus the higher BC.
If you took the same size/shape bullet and magicaly increased its density to, say twice that of lead, the BC would increas accordingly.
Non of this stuff is magic, it all comes down to physics.
Mass x velocity = momentum Which means that two objects of dissimilar mass but equal velocity (assuming the size and shape are identical) will be effected by the forces of drag differently. The object with the larger mass will require more force to slow it down at the same rate as the smaller one, and since the force of drag will be identical for both ( ie, the identical shape and size) it will require more time.
Thus since it requires more time, it can be said to be more efficient, as far cutting through the air anyway. The more time it takes to slow it down the higher the BC.
"Identical shape, identical amount of aerodynamic drag but still a different BC."
The two bullets jwp475 mentioned do if fact have dissimilar shapes. Even though the WC bullet is lighter it is also more aerodynamic. Thus the higher BC.
If you took the same size/shape bullet and magicaly increased its density to, say twice that of lead, the BC would increas accordingly.
Non of this stuff is magic, it all comes down to physics.
Mass x velocity = momentum Which means that two objects of dissimilar mass but equal velocity (assuming the size and shape are identical) will be effected by the forces of drag differently. The object with the larger mass will require more force to slow it down at the same rate as the smaller one, and since the force of drag will be identical for both ( ie, the identical shape and size) it will require more time.
Thus since it requires more time, it can be said to be more efficient, as far cutting through the air anyway. The more time it takes to slow it down the higher the BC.
Jon A
Well-Known Member
steve smith
Well-Known Member
Jon A
I was replying to jwp475, on his request for an explanation on how a lighter projectile can have a higher BC.
He had mentioned the wildcat 265gr and the 300gr Matchking, which have dissimilar sizes and shapes.
But, what i said carries over to the original question Hogslayer had.
"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"
My answer was yes it does change the BC.
But, and there is always a but. Only if the bullets (the 80, 85, 90gr wildcat bullets) have the exact same profile as one another, and the only thing that changed was the mass, will the BC increase in the way i stated.
If the profile/shape does change, then the BC will also change, but not just because of the change in mass.
It is possible that the BC stays the same or even goes down as the mass increases, if the heavier bullet is less aerodynamic than the lighter bullets.
Oh! and my post should have read "IN" and not "if". (The two bullets jwp475 mentioned do "if" fact have dissimilar shapes)
I was replying to jwp475, on his request for an explanation on how a lighter projectile can have a higher BC.
He had mentioned the wildcat 265gr and the 300gr Matchking, which have dissimilar sizes and shapes.
But, what i said carries over to the original question Hogslayer had.
"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"
My answer was yes it does change the BC.
But, and there is always a but. Only if the bullets (the 80, 85, 90gr wildcat bullets) have the exact same profile as one another, and the only thing that changed was the mass, will the BC increase in the way i stated.
If the profile/shape does change, then the BC will also change, but not just because of the change in mass.
It is possible that the BC stays the same or even goes down as the mass increases, if the heavier bullet is less aerodynamic than the lighter bullets.
Oh! and my post should have read "IN" and not "if". (The two bullets jwp475 mentioned do "if" fact have dissimilar shapes)
Jon A
Well-Known Member
Correct. We're on the same page.
