I posted a while back with a joule converter.
I've completed edits to included a Recommended Minimum Engagement Distance and a Theoretical Effective Range Calculator.
This can be used in the field with a Smart Device running Excel or Sheets and is capable of calculating MED from .12 to .43 at 1700 FPS and the Theoretical Effective Range calculation leaves out a lot of factors such as hopup and inner barrel ID and assumes you are firing from a height of 1 meter and the range is flat.
The joule calculation will also turn red if the limit of 1.64 Joules has been exceeded to immediately identify hot weapons.
Take a look at it and see if it helps, thanks!
Joule / MED Calculator