Does velocity affect ballistic coefficient?

Blackdirt Cowboy

Well-Known Member
Joined
Dec 9, 2018
Messages
594
Location
Texas
All right, guys, I need a little more help. I loaded a fresh batch of 50 rounds and headed to the field to double check that I've got everything right before my mule deer hunt.

I started with my bc in the calculator set at .320 from my prior outing. I set up at 500 yards, and missed twice. This caused me a little concern, because this should have been dead on according to my last outing. I moved on to 200 yards to confirm zero and shot a .5 moa three shot group, so my zero is still good.

Next, I moved back out to 400 yards, with my bc still set at .320. I shot a .75” three shot group, dead on the bullseye. As a matter of fact, one shot hit right in the middle of the bullseye. Ok. This is better. Maybe it was my shooting at 500 earlier that was off.

Now I back up to 600 yards. My ballistic calculator, still set at .320, wants me to dial up 5.95 moa. I check the range again with my Sig kilo 2400 abs and it want me to hold 5.94 moa. Perfect. I dial up 6 moa and….miss. Maybe it was poor shooting mechanics, so I shoot again and miss. Hmmm. What’s going on? I’m dead on at 400 and shooting low at 600.

Just out of curiosity, I set the bc back to .230, which is what hammer advertises for this bullet. Now I needed to dial up 6.77 moa. So I dialed it up and shot these two shots…

226DA8FB-F534-4FA9-B493-E76E672E28B1.jpeg


So, what I know is that at 400 yards, my bullet has a bc of .320. At 600 yards, the bc is .230. This is all holding velocity constant at 3635 FPS, of course. So how do I account for this in a hunting situation? Is there a way to make a ballistics calculator account for these differing bc values? I’m sure there won’t be enough time to range a deer, adjust the calculator, dial up, and then shoot.
 

Blackdirt Cowboy

Well-Known Member
Joined
Dec 9, 2018
Messages
594
Location
Texas
That’s what I thought, bean. So I know my zero, 400 yard, and 600 yard data. I guess I really need to shoot 300 and 500 to fill in the blanks and I’ll be ready to go.
 

338 dude

Well-Known Member
LRH Team Member
Joined
Mar 1, 2016
Messages
3,264
Location
Tn
If you are using Applied Ballistics, try the Custom Curve. I've used it my last two guns and not had to true the BC...........yet;)
Why pay for it when it is in Bryan Litz’s book ballistic performance of rifle bullets
image.jpg
 
Last edited:

Calvin45

Well-Known Member
Joined
Apr 13, 2019
Messages
1,247
Location
Nipawin, Saskatchewan, Canada
All right, guys, I need a little more help. I loaded a fresh batch of 50 rounds and headed to the field to double check that I've got everything right before my mule deer hunt.

I started with my bc in the calculator set at .320 from my prior outing. I set up at 500 yards, and missed twice. This caused me a little concern, because this should have been dead on according to my last outing. I moved on to 200 yards to confirm zero and shot a .5 moa three shot group, so my zero is still good.

Next, I moved back out to 400 yards, with my bc still set at .320. I shot a .75” three shot group, dead on the bullseye. As a matter of fact, one shot hit right in the middle of the bullseye. Ok. This is better. Maybe it was my shooting at 500 earlier that was off.

Now I back up to 600 yards. My ballistic calculator, still set at .320, wants me to dial up 5.95 moa. I check the range again with my Sig kilo 2400 abs and it want me to hold 5.94 moa. Perfect. I dial up 6 moa and….miss. Maybe it was poor shooting mechanics, so I shoot again and miss. Hmmm. What’s going on? I’m dead on at 400 and shooting low at 600.

Just out of curiosity, I set the bc back to .230, which is what hammer advertises for this bullet. Now I needed to dial up 6.77 moa. So I dialed it up and shot these two shots…

View attachment 300122

So, what I know is that at 400 yards, my bullet has a bc of .320. At 600 yards, the bc is .230. This is all holding velocity constant at 3635 FPS, of course. So how do I account for this in a hunting situation? Is there a way to make a ballistics calculator account for these differing bc values? I’m sure there won’t be enough time to range a deer, adjust the calculator, dial up, and then shoot.
And this is why plugging numbers into a ballistics calculator and then taking shots at game animals at distances one hasn’t verified on non-living targets is a fantastic way to miss or wound something! Thanks for sharing. Very interesting
 

Blackdirt Cowboy

Well-Known Member
Joined
Dec 9, 2018
Messages
594
Location
Texas
And this is why plugging numbers into a ballistics calculator and then taking shots at game animals at distances one hasn’t verified on non-living targets is a fantastic way to miss or wound something! Thanks for sharing. Very interesting
Exactly why I’m working on verifying everything. I don’t want to be staring at a 180” deer wondering if the calculator is right or not.
 
Top