Dante is correct - certain artillery and rocket launcher units are sensitive to which way they are facing. If they are in range and still not firing then try altering the direction they are facing. Also something to consider is whether you have a number of artillery units in a Group or seperate and whether you have a number of targets in a Group or seperate- Lockon can be a bit odd about whether all units open fire at the first in a Group etc.
EXAMPLE
I set up a group of three SAU Beregs, targeted at a ship. Only one of them (1 of 3) fires on the ship.
If I add a 2nd ship target (a smaller ship so it will sink faster), then 2 Beregs fire, one at each ship. As soon as the smaller ship sinks, the 2nd Bereg (2 of 3) stops firing. Similar with 3 ships.
Then I changed it so that the Bereg's were each in their own group (1 of 1), and of course it takes longer using the Mission Editor to target each of these on the single ship target. Now they will all open fire on the ship.
With two ship targets, they all fire at the first ship till it sinks, then all swap their fire to the second ship.
As for ranges, this is all stuff that I scribbled over the last 3 years in my Lockon notebook, hence some in km, some in Nm, so apologies for that.
Smersh, Grad will fire a spill taking 40 secs / 20 secs respectively then will reload (about 15min?) before firing again.
Gvozdika - 6 rnds per min
Akatsia - 4 rnds per min
Msta - 8 rnds per min
Bereg - 10 rnds per min
Nona - 8 rnds per min
Max ranges Artillery/Rockets
Smersh 70km
Grad 20km
MLRS 31km
M109 15nm
SAU Berg 18.5nm
SAU Gvozdika 15nm
SAU Akatsia 15nm
SAU Msta 15nm
SAU Nona 5.5nm
Max ranges Naval artillery
Ticonderoga 14.5km
Perry 14.5km
Moscow 20km
Neustrashimy 21.5km
Rezky 21.5km
Albatros 6km
Molniya 15km
If you want some arty to bombard an area to add colour to a mission,
1) target a co-ord, so arty keep firing. If you target a building, once destroyed then the arty stops firing.
2) if your arty all in one group, then have same number of targets to ensure each arty in the group has a target to fire at.
3) if you mix the arty types (bereg, msta, nona, etc) then they fire at different rates and looks "prettier"