Home Forums Reloading Big Game Rifles Labradar question

Just an academic question.
How can you use the downrange velocities (25 50 75 100 yds. etc) that the unit displays?

I mean why even have them? Granted if it read the bullet at 300-600 yards you can determine BC (I guess) but why this?

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Why would you assume that the measurements from 0-100 yards couldn't be used to determine B.C.? Yes, calculating B.C. from a 300-600 velocity will give you a more accurate average B.C., but since B.C. changes with velocity the velocity data from 0-100 yards from the LabRadar can give you an accurate initial B.C.

Other than that? If the unit has calculated it, why not show it? What harm is there in it?

No harm at all I just wondered what the idea behind that was.

Good for determining initial BC.

An example is the Hornaday 105gr BTHP states a G7 of 0.253. I enter this into a ballistic calculator, the come ups are not accurate at all, I check the muzzle velocity against the 100 yard velocity and determine the G7 is 0.233 under my conditions (3000 ft elevation) ballistic chart is spot on now.

Another is to determine how much the BC degrades with less than optimal twist for bullet used. example is a 200gr NAB has a BC of 0.273, however in a 1:11 twist barrel it is 0.268. Again the ballistic chart is spot on.

The initial BC seems to work to ~550-600 yards out then starts to wander.