Well as usual the lowly conscripts & militas is getting the shot end of the stick when it comes to shooting.
True they should not shoot as good as a Guard unit but a massed of them will still hit something when you got 400-600 of them firing.
The thing about conscripts & militas is that they had no staying power and would break far sooner than an Elite or Veteran unit.
But if they are at the normal effective range for Muskets (0-100 meter/yards) they will hit things.
I use a Firing table using D10's and it has Close, Medium and Long range.
I also only have four types of troops; Elite, Veteran, Regular & Milita.
So for Muskets it would look like this.
Close Range: 0-100 meters
Elites – 5
Veterans – 5
Regular – 6
Milita – 7
Medium Range: 100-200 meters
Elites – 6
Veterans – 6
Regular – 7
Milita – 8
Long Range: 200-300 meters
Elites – 7
Veterans – 8
Regular – 8
Milita – 9
This is more in line with real world effects.
link
Plus remember that in most rules that round of fire is not just one volley but several since most rules have 20-30 minute turns.
Where it matters is with the quality of troops since the better troops will stand their ground longer.
So militas with their lower morale factor will break far sooner than an unit of Elites.
But you should not have them not being able to hit anything.