I have to open this thread with a disclaimer: the ordnance rules aren't quite right, and when I get around to tweaking them, I'll have to rework what I have here.
That out of the way, what I think we've been missing is a more full treatment of grenade launchers. The way the AToW and Tech Manual rules parse them out, "Compact" grenade launchers only use Class A ordnance (micro-grenades), and they are the only ones to use them. Even more strangely, apparently none of the rifles that sling "Compact" grenade launchers as under barrel mounts actually use the single shot version: they all use either five or six shot versions which aren't listed independently anywhere (per the most recent printing of AToW, pages 266-267).
As for real world grenade launchers, semi-automatic versions existed at least as far back as Vietnam when China Lake built the SEALs a pump action 40 mm grenade launcher (the tube magazine could hold three rounds, and one more could be in the chamber for a total of four when fully loaded). Today, six shot versions with rotary "magazines" are built by several countries, and the Mark 19 Grenade Machine Gun is a perfect analog for the "Heavy Grenade Launcher" (with the obvious exception of its weight; the latter is under half the weight of the real world version). The US Objective Infantry Combat Weapon was prototyped with a 20mm semi-automatic "grenade" launcher that could be seen as an analog for one of the above micro-grenade launchers. The US also experimented with 25 mm grenades, and other countries tried 30 mm and 35 mm grenade launchers.
Given all of the above, it struck me firing mode and ordnance should be independent factors in individual weapon design. Thus, within the game, we should logically have single shot, semi-automatic (i.e., with a magazine size of at least three to get over the Reload Factor in the damage conversion formula), and fully automatic versions at each size of grenade. In the "not quite right" category, the Clan Heavy Automatic Grenade Launcher is listed as using Class D (!) ordnance. If we take 20 mm as being Class A, 30 mm for Class B, and 40 mm (the real world US standard) as Class C, that would put Class D somewhere in the 60 mm range, right up there with light mortars and LAW rockets. In an effort to not change too much before I try to fix ordnance, I'll just roll with Clan tech using "Maxi" grenades as ammunition (I do have a question up about that in the rules forum; if that weapon really uses Class D ordnance, it's "reload" weighs twice what the weapon itself does).
So, without further ado, here's my Grenade Launcher table. It includes single shot, semi-automatic and fully automatic versions at every grenade (ordnance) size. Per the damage conversion rules from AToW Companion (page 170), the listed AP and BD are the average of the types available (among Anti-Infantry, Anti-Vehicle and High Explosive) at that size. I took 40 mm as the size of "standard" grenades, which makes them Class C ordnance. Micros are 20 mm, Minis are 30 mm, and Maxis are 60 mm. For simplicity's sake, I assume any "Semi-Automatic" model has at least three shots to eliminate the damage reduction from the Reload Factor (RF). To get the Class B Launchers close to their current incarnations in the rules, I had to assume a strange burst size (19) for the "Automatic Grenade Launcher". Even doing that, the vanilla "Grenade Launcher" comes out with a little bit more damage than the Tech Manual tables would otherwise indicate (0.85 vs. 0.81 in the table; I've posted a rules question to that effect). To remain consistent with the existing rules, they all have a 1/2/3 range for purposes of the tactical ('mech scale) game. When I revisit this after trying to "fix" ordnance, I'll take another look at that.
Analog Ordnance AP BD PF Burst DF RF Crew TW Damage Weight (kg)
A Micro Grenade Launchers
Flare Gun 20mm Single Shot 3 7 0.75 1 32.9 0.333 1 0.16 3
OICW 20mm Semi-Auto 3 7 0.75 1 32.9 1 1 0.47 4
- 20mm Automatic 3 7 0.75 20 59.5 1 1 0.89 9
B Mini Grenade Launchers
- 30mm Single Shot 4 9 1 1 42.3 0.333 1 0.28 4
BS-1 Tishina 30mm Semi-Auto 4 9 1 1 42.3 1 1 0.85 5
AGS-17/30 30mm Automatic 4 9 1 19 74.7 1 1 1.49 12
C Grenade Launchers
M203 40mm Single Shot 6 10.667 1.5 1 50.133 0.333 1 0.50 5
China Lake 40mm Semi-Auto 6 10.667 1.5 1 50.133 1 1 1.50 6
Mk 19 40mm Automatic 6 10.667 1.5 5 58.667 1 1E 1.76 18
D Maxi Grenade Launchers (Clan)
- 60mm Single Shot 6 11.667 1.5 1 54.833 0.333 1 0.55 6
- 60mm Semi-Auto 6 11.667 1.5 1 54.833 1 1E 1.65 10
- 60mm Automatic 6 11.667 1.5 5 64.167 1 1E 1.93 20