Drop Chart Trajectory

[Belton45]

I am pretty new to ballistics and calculating drop charts. I was playing with one of my AR’s today. Shooting 77 SMK I was getting 2635 fps. I loaded that data in to JDM ballistics calculate and it spit out info below. Seem rite? Anyone recommend a different calculator? Thanks.

 

[Rob01]

JBM is real good. I have used their data for years for matches and still do for some rifles. I would get rid of the inches in the column and if it's an MOA scope make them both MOA or the same for mils. You have the sight height good which is something people forget and usually leave at 1.5".

 

[6ShotsOr5?]

You have target speed set to 10 mph which is probably not what you wanted. Usually that would be zero.

 

[Rob01]

Actually that would depend on the target speed if shooting movers. It's irrelevant if not shooting movers.

 

[Belton45]

You have target speed set to 10 mph which is probably not what you wanted. Usually that would be zero.

Thanks. Did not notice that.

 

[Rob01]

Thanks. Did not notice that.

You shooting movers?

 

[Belton45]

You shooting movers?

Nope. Just punching paper.

 

[Rob01]

Nope. Just punching paper.

Then that could be 100MPH and not matter as it only shows up in the lead column over to the right. LOL No need to change it unless shooting movers and then set the approximate target speed.

 

[Rob01]

One other thing. Use the Trajectory Simplified page on JBM. It has all you need for data and a lot less of the columns that confuse most and aren't really needed.

JBM - Calculations - Trajectory (Simplified)

jbmballistics.com