BC at extreme velocity

[Luke45]

So in my understanding, BC usually goes up at higher velocities say in the jump from 2000 to 2500 fps and up again from 2500 to 3000 fps( like Sierra who states BC values at certain vrlocity) I have not, however, seen BC values for >3500 fps.

does BC of a bullet continue to go up from say 3000 fps to 3500 or 4000 or 4500 fps? Or do BC values platoe?

shooting 53 gr vmaxs with a .29 G1 BC , there not dropping as much as my calcs say, seeing if I'm off on a variable or if the BC is higher than I thought due to the extreme velocity of a 22-250 ai?

thanks!

[LoneWolf]

I don't have an exact answer for the question about BC. Ballistic Calculators and chronys provide and get some good data, but the most accurate way to get drop data will always be going out shooting different distances and collecting it the old fashioned way.

I use strelok+ on my android phone and it's very good, but still had to adjust the data it was providing for my 308 when I got out passed 700yds. Of course there are many other variables that can play into the equation the further the distance is that you are shooting at.

[Luke45]

Definitly, more of a curiosity thang that any. I've rarely owned a rifle that shoots more than 3000ish fps, so it's never really crossed my mind untill this 22-250, it's not a huge difference just about 2" less drop at 500, trying to see if msybe it is BC related due to the high velocity, since I know BC usually trends higher as velocity increases

[darkker]

Problem is that your answer isn't exactly simple.
Drag is proportional to the square of velocity, However... Way more factors are at play than just that.
The "steps" you see in listed G1 BC numbers are as much a description about the change in air flow around the bullet, as it is a simple description of "slipperyness".
All bullets fired have a natural yaw to them, and procession around the center of rotation. Those factors also play a role, as a sideways skidding bullet isn't very efficient; regardless of how sleek it may be.

More specifically to your specific bullet question: Your bullet looks nothing like the standard G1 projectile, and you are only given ONE G1 BC number, which doesn't exist. Should you really be surprised that the numbers don't jive? No.
So: how did Hornady come up with that number? Did they fudge it based on a mathematical calculation? Did they take an average of observed results? If so, over what set of distances?

For the overwhelming bulk of Non-hunting bullets (flat base, round noise types) G7 ratings are MUCH closer to reality, until trans-sonic. At that point the flow of air around the bullet shows the G1 system to work very well, regardless of bullet shape.

[scope eye]

So in my understanding, BC usually goes up at higher velocities say in the jump from 2000 to 2500 fps and up again from 2500 to 3000 fps( like Sierra who states BC values at certain vrlocity) I have not, however, seen BC values for >3500 fps.

does BC of a bullet continue to go up from say 3000 fps to 3500 or 4000 or 4500 fps? Or do BC values platoe?

shooting 53 gr vmaxs with a .29 G1 BC , there not dropping as much as my calcs say, seeing if I'm off on a variable or if the BC is higher than I thought due to the extreme velocity of a 22-250 ai?

thanks!

I have been advocating this theory for years, based on my own personal experience every time I shoot, my bullet drop and drift are not even close to the data given, on these BC calculating charts and apps, if you thing the numbers don't add up at 3500 fps, you should see them at 4500 plus fps, I have come to the conclusion that time of flight is also a factor in this equation, like I have always said "a bullet that spends less time in the wind will be less affected by the wind" I see it every time I pull the trigger.

Dean

[stomp442]

I think the problem your seeing is the fact you are using a G1 standard BC instead of a G7 for that particular bullet. The G7 is much more velocity consistent. According to my quick calculations using the formula found in Brian litz book applied ballistics for long range shooting. The G7 BC for that particular bullet should around .149 - 151 depending on its drag profile. Use that in your calcs and see if it makes things match up better.

[Robinhood]

What is your elevation?

[Luke45]

thanks Stomp! i have the Litz book, but it must be an old book becasue the 53 gr vmax is not in it.

robinhood- 5500 ft