[Emperor's Child]

I think you guys have helped me solve this. While I can't actually make the weapons hit at a 50% rate, I can change the damage tables to make them give damage at that rate.

As long as I keep the base percentage to hit some value other than the minimum all the way out to the max weapon range, I can scale the one weapon's damage to have the same effect. In single ship or small unit engagements it may be less of a constant depending if you land a few hits at long range quickly, but in larger battles and over the long haul the result should be close.

My max weapon range is 12, and my intended value of to-hit in that range for normal weapons is 75% at point blank to 25% at max range.

I'll change the system settings to the following:
Combat Base To Hit Value := 75
Combat To Hit Modifier Per Square Distance := 4

This will give me the following percentage to hit:
Range............1...2...3...4...5...6...7...8...9 ..10.11.12
Base %to hit 71 67 63 59 55 51 47 43 39 35 31 27

In order to correct a weapon to give an average damage as if it were hitting 50% of the time, the damage would need to be changed by the following percentage:

Range.................1...2...3...4...5...6....7.. ..8.....9....10...11...12
Damage % mod 70 75 79 85 91 98 106 116 128 143 161 185

Thanks guys, I think this will get me close enough to make it work.