# Reply To: BC: Our GA Drag Model/ Drag Coefficient

Forums › Pellets, Projectiles, Slugs, & Ammo › BC: Our GA Drag Model/ Drag Coefficient › Reply To: BC: Our GA Drag Model/ Drag Coefficient

JungleShooter

BC: Our GA Drag Model/ Drag CoefficientThere was some interest in the GA drag model for airgun pellets. This, together with a pellet's ballistic coefficient (BC), helps our ballistic calculators give us holdovers and holdoffs.

I found the GA drag model:

Strelok Pro has an option to enter custom drag profiles, and when going to that function the user can choose to "email" the data — and in reality it is a "share" option.

The content of the text file (.txt) that Strelok gives me is

listed below.The first number in each line is the drag coefficient (Cd), the second the mach number (though when entering this data in Strelok manually these are switched around).

However, if I understand the pro ballisticians correctly,

finding the custom drag model (CDM)for a projectile is much more accurate than one fixed BC with a one-fits-all drag model — mainlyrelevant for long-rangeshooting (100y and up).

I'm planning to find the CDM for a couple of pellets in the next months (a bunch of pellets over a chrono at various ranges, don't have no LabRadar). Got any advice for me?

Matthias

CFM, GA, 0.0, 0.0, 0.00000, StrelokPro, 0.000, 0.000, 0.000, 0.0

Chairgun GA retardation table for Diabolo Airgun Pellet

0.250 0.000

0.235 0.100

0.221 0.200

0.207 0.300

0.196 0.400

0.189 0.500

0.189 0.600

0.202 0.700

0.241 0.800

0.329 0.900

0.488 1.000

0.597 1.100

0.649 1.200

0.669 1.300

0.672 1.400

0.667 1.500

0.657 1.600

0.644 1.700

0.630 1.800

0.616 1.900

0.602 2.000

0.589 2.100

0.577 2.200

0.566 2.300

0.556 2.400

0.548 2.500

0.540 2.600

0.534 2.700

0.529 2.800

0.524 2.900

0.521 3.000

0.521 3.100

0.517 3.200

0.514 3.300

0.510 3.400

0.507 3.500

0.503 3.600Mod Edit: moved to Pellets, Projectiles, Slugs and Ammo forum

I can’t quite tell simply by looking at the numbers but have you happened to evaluate to find out if the drag coefficients are linear between 0 and Mach 1.2? I suppose I could graph them but then…..work. ðŸ˜‰

JungleShooter

BC: Our GA Drag Model/ Drag CoefficientThere was some interest in the GA drag model for airgun pellets. This, together with a pellet's ballistic coefficient (BC), helps our ballistic calculators give us holdovers and holdoffs.

I found the GA drag model:

Strelok Pro has an option to enter custom drag profiles, and when going to that function the user can choose to "email" the data — and in reality it is a "share" option.

The content of the text file (.txt) that Strelok gives me is

listed below.The first number in each line is the drag coefficient (Cd), the second the mach number (though when entering this data in Strelok manually these are switched around).

However, if I understand the pro ballisticians correctly,

finding the custom drag model (CDM)for a projectile is much more accurate than one fixed BC with a one-fits-all drag model — mainlyrelevant for long-rangeshooting (100y and up).

I'm planning to find the CDM for a couple of pellets in the next months (a bunch of pellets over a chrono at various ranges, don't have no LabRadar). Got any advice for me?

Matthias

CFM, GA, 0.0, 0.0, 0.00000, StrelokPro, 0.000, 0.000, 0.000, 0.0

Chairgun GA retardation table for Diabolo Airgun Pellet

0.250 0.000

0.235 0.100

0.221 0.200

0.207 0.300

0.196 0.400

0.189 0.500

0.189 0.600

0.202 0.700

0.241 0.800

0.329 0.900

0.488 1.000

0.597 1.100

0.649 1.200

0.669 1.300

0.672 1.400

0.667 1.500

0.657 1.600

0.644 1.700

0.630 1.800

0.616 1.900

0.602 2.000

0.589 2.100

0.577 2.200

0.566 2.300

0.556 2.400

0.548 2.500

0.540 2.600

0.534 2.700

0.529 2.800

0.524 2.900

0.521 3.000

0.521 3.100

0.517 3.200

0.514 3.300

0.510 3.400

0.507 3.500

0.503 3.600Mod Edit: moved to Pellets, Projectiles, Slugs and Ammo forum

I can’t quite tell simply by looking at the numbers but have you happened to evaluate to find out if the drag coefficients are linear between 0 and Mach 1.2? I suppose I could graph them but then.....work. ðŸ˜‰