Akmtnrunner
Active Member
- Joined
- Oct 11, 2015
- Messages
- 29
I'm coming here with some BC questions since I figure you folks are knowledgeable on the subject. I did call Swift with this question and got a prompt call back from one of their technicians/ballisticians, although I am not sure if I buy his explanation. I'm hoping to hear some other educated opinions on the subject.
So here's the deal. My choice hunting bullet is Swift's .375 caliber A-Frame in 300 grains. Swift also has .375 caliber A-Frames in 250 and 270 grains. Same construction, same nose, ogive, and flat base shapes, just longer shafts in the heavier bullets.
So, I would think the heavier bullets would have higher BC's along with their higher sectional densities. Except, their BC's go like this:
375 Cal:
250 grain) BC 0.254
270 grain) BC 0.349
300 grain) BC 0.325
Their 9.3 Caliber bullets do the same thing:
250 grain) BC 0.285
286 grain) BC 0.385
300 grain) BC 0.342
Graphics of the bullets are here: Products
Why would the BC of either 300 grain version decrease from the middle weight version? Again, same nose, ogive, and base shapes.
The technician's explanation was that the BC's change according to speed and each bullet weights BC's were calculated with different velocities. I think he mentioned around 2850 for the 375 cal 250gr, and 2600 for the 300gr. Okay, I know that to be true. But why wouldn't that affect the other calibers too? In every other caliber, their A-Frame and Scirocco bullets' BC always increase with greater weight. Could there be something else at play?
My hunch is their BC's are mixed up between their middle and heavy weights. But the guy swore they were correct.
I know I don't need to be really concerned with the BC's of these hunting bullets for my 375. I'm not going to use these past 250 yards and I will probably never tell the difference on target. But this does bug me. I am stickler on reducing the risk of anything wrong happening.
Someday I will true the bullet's BC for my rifle to get the most valuable numbers, but I'm hoping I can also learn something from folks much more knowledgeable on the subject than I am. I appreciate your help.
So here's the deal. My choice hunting bullet is Swift's .375 caliber A-Frame in 300 grains. Swift also has .375 caliber A-Frames in 250 and 270 grains. Same construction, same nose, ogive, and flat base shapes, just longer shafts in the heavier bullets.
So, I would think the heavier bullets would have higher BC's along with their higher sectional densities. Except, their BC's go like this:
375 Cal:
250 grain) BC 0.254
270 grain) BC 0.349
300 grain) BC 0.325
Their 9.3 Caliber bullets do the same thing:
250 grain) BC 0.285
286 grain) BC 0.385
300 grain) BC 0.342
Graphics of the bullets are here: Products
Why would the BC of either 300 grain version decrease from the middle weight version? Again, same nose, ogive, and base shapes.
The technician's explanation was that the BC's change according to speed and each bullet weights BC's were calculated with different velocities. I think he mentioned around 2850 for the 375 cal 250gr, and 2600 for the 300gr. Okay, I know that to be true. But why wouldn't that affect the other calibers too? In every other caliber, their A-Frame and Scirocco bullets' BC always increase with greater weight. Could there be something else at play?
My hunch is their BC's are mixed up between their middle and heavy weights. But the guy swore they were correct.
I know I don't need to be really concerned with the BC's of these hunting bullets for my 375. I'm not going to use these past 250 yards and I will probably never tell the difference on target. But this does bug me. I am stickler on reducing the risk of anything wrong happening.
Someday I will true the bullet's BC for my rifle to get the most valuable numbers, but I'm hoping I can also learn something from folks much more knowledgeable on the subject than I am. I appreciate your help.
