I haven't figured out how to fix ordnance yet, but mortars have been on my mind, so I decided to give them a shot. The main problem with them (aside from ordnance) is range: real world mortars have ranges measured in kilometers, not meters. Light (60mm) mortars are effective out to about 3.5km, mediums (81mm in real life, 90mm below for aescetics) to ~6km, and heavies (120mm) ~7km.
The ordnance problem can be mostly chalked up to blast radius and the rules for explosive (type X) damage in ATOW.
Real world blast radii would drive ridiculously high damage values even for the 60mm round (i.e., higher than what I propose below).
Fortunately for the heavy mortar, BA Tube Artillery seems to be an attempt to capture it. Aside from its range and only being available to BA, I think it does a decent job.
The AP and BD values in the table below represent HE only. I'm holding off on doing anything else until I figure out a fix for ordnance overall.
Weight (kg) Max Min
Analog Bore Weapon AP BD PF Burst DF RF Crew TW Dmg Weapon Reload Range Range
M224 60mm Light 6X 16 1.5 1 72 0.33 2 0.72 20 2 8 maps 3 hexes
M252 90mm Medium 8X 17 2 1 76.5 0.33 3 1.02 40 4 12 maps 3 hexes
M120 120mm Heavy 10X 18 2.5 1 81 0.33 5 3/1 150 15 16 maps 21 hexes
EDIT: I found two things that change my math above. 1)
Herb's errata for the conversion formula that rounds the burst factor, and 2) the rules for converting TW area effect damage to AToW (page 213 in AToW). There's a bit of strangeness there due to how they implement the blast attenuation. It's clearly made for "real" artillery, so it doesn't quite work as written for a 3/1 damage profile, but I've adjusted the above as follows:
Heavy Mortars: Instead of using the page 213 -1AP/-4BD per meter after 15 meters from the target TW hex (with the base damage steady out to that point), I'm going to use -1AP/-1BD per meter as usual for AToW damage (but still starting 15 hexes out from the TW hex). That means at 60 meters from impact, a heavy mortar would do 3BD (enough to qualify for that 1 point of TW damage in the surrounding TW hexes, I think). Basically, the damage profile looks like: 10X/18 out to 45 meters from the 1-meter AToW point of impact, then -1AP/-1BD until damage is 0 (at 63 meters from the AToW point of impact).
Medium Mortars: I'm aiming for Medium mortars to do 1 point of TW damage as an AE weapon on the TW hex scale (covering just one hex). I think the usual -1AP/-1BD figure from the 1-meter impact hex can get there starting from 8X/17.
Light mortars have a bit of a boost beyond ordnance as written to ensure they do damage of some kind out to 14 meters (and be able to inflict one point of damage to an armored target with a near miss; i.e., within 1 meter), but won't be Area Effect at the TW scale.