You would be surprised how much having an active 1=1000 Mil unit is usefull in gunnery. My first calculations for a 2k mark in my Revi16 for the 5 B,K was spot on. I have a copy of the AAF 75mm gunnery chart to 5k.
M4 Shell M48, 75mm HE
3000ft, 250IAS, 8.74sec, -980ft, 5000yd
CV = aprox 33.38 m long.
1 @ 1000 = ??

The A1 bombing head with the 14 degree adjustment in the B25H was adjusted based on alt and speed to fire at shipping from 4k away. The copilot read off a plotting chart for the pilot. How do you determin range by the target ship? How do you determin loft to place the 75mm round 4k down range? It's about -50Mil to shoot 4k and -71Mil to shoot 5k. CV is 9Mil at 4k and 7Mil at 5k. How far will the ship travel in 6.87-8.74 sec?
With a chart of time, distance and drop at distance. Knowing the size of your target you can generate a Mil chart for your gunsight in the game. Oh thats that 1=1000 unit. Or build a gunsight with a Mil gradient to assist you in determining the range to the target and asmuth to fire with.
Hey this is just a kiddy game. Kentucky windage is all you need. The CV is the width of your thumb about 2k. The 5inch gunners in the fleet will enjoy your efforts while you Picasso your way to glory. Using your thumb used to be a way to copy scale in the early days of perspecitve painting. Early 1=1000 units.