Range Report Question About JBM

[Pete E]

Just been playing about with the various calculators on the JBM.

In particular I was putting some data into the Range Card calculator and I got the results blow:

Trajectory Card
Range ---Drop-------Wind------Lead
(m) (mil) (mil) (mil) (mil) (mil) (mil)
100 -0.0 -0.0 0.0 0.0 0.0 0.0


I did not put in an value for wind or lead, hence why they are "0.0" but why is there two columns under each heading? Is it so you can set it up to the results in say two units ie "Mils" and "CM"???

Also it asks for Lowest Temp and Lowest Velocity and Highest Temp and Highest Velocity...

Does this mean to get accurate results you have to measure the temperature for each shot? And what temp are you measuring? Air temp? Barrel temp at the muzzle? or something else?

Regards,

Peter

 

[Lindy]

Re: Question About JBM

Look down near the bottom of the page, and you'll see pick boxes labeled, "Drop units (1st column)" and "Drop units (2nd column)".

When it's asking for the temperature data, that's so it can calculate the change of muzzle velocity with temperature. It's for a low temperature/muzzle velocity pair, and a high one. If you haven't measured that, don't use it.

 

[Pete E]

Re: Question About JBM

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">
When it's asking for the temperature data, that's so it can calculate the change of muzzle velocity with temperature. It's for a low temperature/muzzle velocity pair, and a high one. If you haven't measured that, don't use it.
</div></div>

Thanks Lindy...Still not sure abut the temp thing though..

Are they talking about taking a simple air temp for each shot?

Or are they refering to the temp of the muzzle after each shot?

Regards,

Peter

 

[Lindy]

Re: Question About JBM

Air temperature, and assuming that the barrel and air temperature are the same.

Each of those pages has a link on it which says "Terms". Click on that link for explanations.

 

[Pete E]

Re: Question About JBM

Lindy,

Thanks again...I did try the link for an explaination, but got a little confused when he mentioned cooling his bullets using ice-water..

Regards,

Peter