Range Report Setting up LB3

[Bearwalk]

I just invested in LB3. So, while new to this particular program, I am very familiar with exterior ballistics analysis, which is my way of saying - dispense with the niceties and give it to me straight.

My questions are regarding setting up LB prior to having a lot of field data with which to tweak. I am interested in getting in the ballpark, now, to provide a good foundation for subsequent adjustments to match field data.

That said, in the ballistics module, LB asks for a G1 or G7 BC as well as a drag coefficient. My understanding that a BC corresponding to the velocity realm of your muzzle velocity is the place to start here. Is this a correct understanding? Secondly, does the program assume that this BC is referenced to ICAO, sight-in or field conditions?

As for the Cd, I again assume that this should correspond to your muzzle velocity. But, I also understand that this is not a true Cd in the classic sense of the term, but rather a retard rate on the BC, i.e the slope of the drag curve. Is this correct? Again, what conditions is this Cd referenced to?

Finally, do you guys find yourself tweaking the BC, Cd, or both, in LB3 to match field data? Any practical lessons here would be appreciated.

I understand that I may be better off directing these questions to PB, but I know that there are a lot of LB gurus on this site and thought I would start here.

 

[Eaglet]

Re: Setting up LB3

Since no gurus are showing up, I'll try to help by passing on to you what has been passed on to me.

<span style="font-weight: bold">I know most of us don’t like to read the “User Manual”, but much of what you’re asking is explained there.
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1) To get the most benefit, you need to define a TRACK

2) That implies to know the atmospheric conditions during SIGHT-IN

3) Yes, it’s based on ICAO for BC and DC

4) In the manual is a small list of standards used by some bullet manufacturers… It’s a good idea to ask the manufacturers.

5) The default value of DC=0.500 works very well for most cases. If you’re using a good solid BC you will almost never have to change it.

6) The DC is an excellent indicator of the quality of the BC

7) If in order to get a “field match” the DC has to be changed more than +/- 10%, then doubts are in order in reference to how good the BC is

8) The BC defines the shape of the Drag’s curve while the DC allows for the fine adjustments of the same.

9) With the theme of DC, would not be easy to determine with precision due to other parameters involved

10) The best is to insure that the BC has been well determined

It's great you asked the question here to allow others to benefit. Trusting, that is, that the answers are right...