Range Report Equation used by Leupold's "True Ballistic Range"

[ctressler]

Does anybody know the equation or method used by Leupold to get their "True Ballistic Range" as measured by their range finders?

There must be a little more to it than the horizontal distance to the target, as they report the "True Ballistic Range" of a 400 yard target at 40 degrees is 335 yards, and the "True Ballistic Range" of a 40 yard target at -40 degrees is 34 yards.

It would appear that they are using the Tangent function to get these results which makes no sense.

 

[SOC308]

Re: Equation used by Leupold's "True Ballistic Range"

I have no idea what leupold uses, but based on what I learned in school:

if you measure 400yds @ 40 degrees

cosine 40 = true range divided by laser range

so we can basically say
True range = cosine 40 * laser range

which comes out to be about 306 yards. To get your range of 335 you would be shooting about a 33 degree angle

 

[doc76251]

Re: Equation used by Leupold's "True Ballistic Range"

They are probably using Sierra's angle formula (which works really well BTW).

Cheers,

Doc

 

[TiroFijo]

Re: Equation used by Leupold's "True Ballistic Range"

They are using the sierra method (I confirmed this with the designer, Bill McDonald, also designer of the sierra infinity program), BUT if you want the ultimate accuracy at long range the ballistic profile of your load must match the selected one closely or you'll still get significant errors at long range.

To see the sierra method, and the comparison with other methods:

http://www.exteriorballistics.com/ebexplained/article1.html

 

[ctressler]

Re: Equation used by Leupold's "True Ballistic Range"

I've read the paper and I don't think it presents the "Serria Method" that Leupold is using, since the Leupold range finder reading does not take into account bullet drop. What is the Serria Method without using bullet drop?

 

[TiroFijo]

Re: Equation used by Leupold's "True Ballistic Range"

You have to select a certain bullet trajectory profile, and this of course includes bullet drop.

Like I said, I personally checked this with the designer...

 

[ctressler]

Re: Equation used by Leupold's "True Ballistic Range"

Makes sense, thanks for the info.

 

[freeflight]

Re: Equation used by Leupold's "True Ballistic Range"

Good to know.