CDS BC help.

[utah400elk]

LEUPOLD CDS help.

looking for a little help with a CDS. I am shooting an Arrowhead XLD muzzleloading bullet.

I get and average velocity of 2029 fps @12 yards and an average 100 yard velocity of 1870 fps.

my math shows a BC of .395 but that seems very high. Anybody have any insight?

The range conditions were:

95°
429 elevation
57% humidity
30.23

Thanks for any help…

 

[std7mag]

I'm taking it this is the 45 caliber, 275gr bullet?
Arrowheads website claims G1 BC of 0.355 @ 2,800fps.
With your lower velocity it would be lower.

Of course knowing caliber & bullet weight would help tremendously!

 

[ImBillT]

Use the actual scope you’re getting the CDS dial for. Zero at every range you want on your dial. If they won’t mark the dial based on those numbers, then back calculate the BC based on drops rather than measured velocity. I don’t know why Leupold would not allow you to say I need 150 at X minutes from yds, and 200yds and Y minutes from 150yds, and 250yds at Z minutes from 200yds. That’s better than fooling with BC crap anyway.

 

[buffybr]

I'm not sure how the CDS turret would work with the B&C reticle.

I have Leupold scopes with CDS turrets on several of my rifles, but they all have the Wind Plex or Duplex reticles. I sent all of the ballistic data to Leupold for my .300 Weatherby, and Leupold marked a turret for that data

For my other CDS scopes, I range verified the bullet impacts at ranges of 200, 300, and 430 yards, and I marked the top of the turrets for those ranges. This has proved very accurate for those rifles.

For my .257 Ackley with the B&C reticle, I zeroed the center cross wire at 2" high at 100 yards, then verified the bullet impacts at 200 yards for the 2nd crosswire, 300 yards for the 3rd crosswire, and 430 yards for the lowest crossswire. I then have a scope sheet that lists the + or - impacts in inches at each crosswire.

This turns out to be Kentucky windage with the lower crosswires and yardages between the crosswires, but the holdover inches are smaller numbers than they would be with a standard single crosswire.