I posted this same question on another site and am curious your experience.
Question on verifying velocity
- Thread starter rcol317
- Start date
Help Support Long Range Hunting Forum
After I find the speed of the bullet by using the Magnetospeed I calculate drop at various ranges for the bullet I'm shooting and then shoot multiple distances to verify if the drops is equal to my calculations. Both cases the drop indicated by shooting distances indicated 100 feet per second faster than the magnetospeed showed.
Have you adjusted for EVERY possible variable ?
Have you shot premium factory ammo and compared your calculations to the factory data ?
It's really immaterial as you set up your range card for your results.
That's why I'm buying the new Swaro --- load the profile, push the button and shoot.
Have you shot premium factory ammo and compared your calculations to the factory data ?
It's really immaterial as you set up your range card for your results.
That's why I'm buying the new Swaro --- load the profile, push the button and shoot.
dok7mm
Well-Known Member
I would verify that you are using the correct B.C. in your ballistic app, as velocity is not everything.
Doom2
Well-Known Member
In addition to the environmental factors including consideration of mirage, one of the things that has to be understood is that the published BC, whether G1 or G7 is a representation of that factor over some velocity range, which often is undefined. Both G1 and G7 refer to drag models for specific projectiles. These model do not typically model the projectiles being shot correctly over a significant range of velocities. The G1 model is actually based on a flat based projectile while G7 is for a boat tail spitzer.
Due to the lack of sensitivity of the trajectory at shorter ranges, it is often recommended to use the published coefficient at ranges less than 600yds and adjust velocity to match dope, and to use measured velocity and adjust BC to match your dope at greater ranges.
Due to the lack of sensitivity of the trajectory at shorter ranges, it is often recommended to use the published coefficient at ranges less than 600yds and adjust velocity to match dope, and to use measured velocity and adjust BC to match your dope at greater ranges.
rammac
Well-Known Member
What you call "data verification" is commonly referred to as "truing" the ballistics curve.
The problem is pretty obvious, if you have confidence that the chronograph (Magnetospeed) is accurate (and as a product it is very accurate) then the only answer is that your BC values at various velocities are wrong (which is a common problem among bullet manufacturers). Bryan Litz provides BC values over a range of velocities for a large selection of bullets. His BC values were obtained through actual field testing using a radar system.
What ballistics engine are you using? If you are using a program that only accepts a single BC value then you will find errors in the estimated drop at longer range. A good program will accept several BC values which are separated by a range of velocities. Having multiple BC values will help tune the trajectory curve of your program to be more accurate.
Check out his book "Ballistic Performance Of Rifle Bullets" to find his BC values. Or, if you want, post the bullet information (manufacturer, brand, weight) and I or someone else could provide you with his BC values.
The problem is pretty obvious, if you have confidence that the chronograph (Magnetospeed) is accurate (and as a product it is very accurate) then the only answer is that your BC values at various velocities are wrong (which is a common problem among bullet manufacturers). Bryan Litz provides BC values over a range of velocities for a large selection of bullets. His BC values were obtained through actual field testing using a radar system.
What ballistics engine are you using? If you are using a program that only accepts a single BC value then you will find errors in the estimated drop at longer range. A good program will accept several BC values which are separated by a range of velocities. Having multiple BC values will help tune the trajectory curve of your program to be more accurate.
Check out his book "Ballistic Performance Of Rifle Bullets" to find his BC values. Or, if you want, post the bullet information (manufacturer, brand, weight) and I or someone else could provide you with his BC values.
Exactly I too will be glad to look up a bullet for anyone just let me know
Thanks for the info. Probably BC issue, I use Ballistic AE app. BC data is from Berger but I've always seem BC's differ when I shoot longer ranges. Just was shocked at both rifles experiencing same results at the same time. In the past I've had to adjust dope at the longer ranges and always assumed it was BC issues.
rammac
Well-Known Member
The third edition lists the data for 724 bullets from .172 thru .510 caliber. Bryan Litz helped develop and popularize the current hybrid bullet design so he does a nice job of including most of the popular long ogive bullets.
I have that book, I'll compare with the data in the Ballistic AE app.
I have the first and the third edition I do not know if they have a fourth edition yet but unless it does come out very recently I'm sure it's in there
Tell me what bullet I will look it up for you
