PDA

View Full Version : JBM Miscalculation


wildcard
05-27-2009, 7:48 AM
Without biasing your opinion with my own formulas.. does it look like their calculations for leading a moving target is completely wrong? I'm specifically looking at it expressed in MILs.

Timberwolf
05-27-2009, 8:10 AM
I always use programs like that as a reference point only. Nothing beats real world dope.

ar15barrels
05-27-2009, 8:14 AM
What's your formula?
I always just looked at time of flight and object speed and back-figured the lead from that.
Works for me...

Off the topic though, which Nighforce do you have, mil/mil or moa/moa?

wildcard
05-27-2009, 8:53 AM
What's your formula?
I always just looked at time of flight and object speed and back-figured the lead from that.
Works for me...

Off the topic though, which Nighforce do you have, mil/mil or moa/moa?

Yup.. my formula is based on the time of projectile travel, target speed, and of course target distance. Specifically the lead in MILs is (in Excel format):

=((TIME OF TRAVEL*SPEED OF TARGET IN FPS*12)-6)/(DISTANCE IN YARDS*0.036)

It will yield a result that doesn't appy for short range or really slow moving targets.. but it has worked perfectly for me for what we apply it to.

I could think of a few other ways to calculate it.. but this seems to work! No reason why your most basic math or physics formulas wouldn't work also as long as you know the time of projectile travel.

Formula was borrowed from Mike R. Lau who I think borrowed it from somewhere else.

My NF scope is MIL/MIL.