LRMs are a pretty light warhead, so I could definitely see an LRM 20 killing "only" 4 guys when the infantry have cover.
Light Warhead, sure, in KG. But, what kind of explosives were they using again? And, besides, LRMs don't do the /10 divisor thing that direct fire weapons are stuck with. On average, an LRM-5 will catch 3 guys in bush, and 6 out in the open.
If you don't like forcing someone to take a full ton of AP ammo for an AC, why not just house rule that you can mix special ammo types in a single ton of ammo rather than create an all-new set of rules?
Because we've already made other changes for games set in this 'alternate setting'. We already have other middlegrounds taken between BT and TW.
For example: Partial cover still grants a +3, but all leg shots are applied to the appropriate arm instead on a full chart role instead of using the Punch table.
Another Example: We split up two different approaches to balancing the hover nerf among the Inner Sphere and Clan technologies. Clans effectively ignore the type modifier, but still have to check for sideslipping, and failure only drifts one hex, as per sideslipping for VToLs in the BMR. IS Hovertanks still track the type modifiers on the motive damage chart, but don't have to roll for sideslipping. They're much more nimble, at the sacrifice of durability.
We use everything from TW combat for civilian gear and support vehicles, though the Partial cover mod is still +3.
We did this as an experiment, using ideals and aesthetics to create an 'Ideal BattleTech' that could still bridge the two rules sets we are familiar with. (I'm sorry, but TW is not ideal, as far as I'm concerned, especially when trying to mesh with fiction.) We decided to treat the BMR rules as 'height of the Star League' for some of the effects one can find, like popping tanks on a high crit roll, or clearing woods rather effectively.
One of my ideals is that damage to infantry should always be random, even from other infantry. I actually see infantry as being rather mobile, and catching a guy is still a matter of random luck, no matter how accurate or intuitive a gunner/control computer might be.
(There's a cheap little board game that I can't remember the name of that was a spoof off of Doom and other FPS computer games. It had an effect (Hack?Cheat) card called 'He Zigged When He Should Have Zagged'. That applies to infantry on the move in a fire zone, as far as I see it.) Because of that, chances of nailing more than one or only one are just as likely, as far as I see it.
As such, since we've already played around with the other rules, trying to apply a randomized structure to infantry is another ideal. However, most of my early thoughts on the matter revolved around a single d6 with its flat randomness. I didn't like it. It would invariably end with something too complex to easily remember.
BT is supposed to be a game of futuristic combat. I've accepted that munitions between cannons of a like class, though variable in diameter, were possible because ACs can be modified rather easily to match the new diameter. Just because it's not possible now, doesn't mean it can't be done in the future.
If I can accept that, I can also accept standard ammo as being programmable and variable in function as the next magazine is being loaded into the weapon - IE: in the middle of combat. To defeat armor takes a different set of characteristics than to kill infantry.
AC munitions were stated to be both High Explosive and Armor Piercing. Under the BMR, the ACs were able to effect both armor and personnel equally effectively. One can attribute this to control computers creating a good spread or tight focus as desired. One can also attribute this to the dual role of the AC munition. Or, you can even assume that the round could change rolls of its own accord, based on input from a computer before being fired out the barrel. This complexity would help explain the costs for munitions beyond powder and metal.
Either way, to be that effective against infantry, you need an HE kick, or really good accuracy.
Experiment, if you're willing and able: Take a semi-automatic rifle. Find some small targets, like, say, Dark Age figures. Put them in some middling tall grass. (Stuff which hasn't been mowed in a while, not necessarily prairie.) Where you can find them. Take aim of the general area and start puling the trigger as fast as you can. Once done, go find your figures and see what damage you've done.
Result: Most likely, you'll not have hit anything you couldn't see.
Try it again, but where you can see them. Still see how many you can hit. Probably more than before, but still not all, under such rapid-firing conditions. Not unless you're a robot. BT MGs are controlled by robots. (A computer tied to servos is still a robot.) A friend pointed out when we tried this experiment that HE would counter such misses. BT ACs are supposed to have HE already in them. They, too, are tied to robots. They should be catching a lot of guys, whether in cover or out in the open. Especially if their protective gear isn't complete, like most BT Infantry are depicted.
The Succession Wars were supposed to see a decline in technology from its height. Look at the effects of TW from the BMR, and you can see a similar theme. In the BMR, weapons from armored units could hit the same number of guys with mechanical regularity. Total Warfare, you're lucky if the machine can increase the diameter of its spread. The effects in Total Warfare seemed idiotically extreme for tech degradation. Thus, the attempt at something in the middle.
If we assume that the robot controlling the weapons isn't as effective as that from the height of technology, then, it stands to reason that it can get a spread, but is still relying on luck to catch the optimum number of guys, and will only manage something less.
Hence the idea that randomized damage to infantry is a middle ground between the BMR and TW.
The optimal spread would be the one out in the open, which is double the standard weapon damage.
I hope all that explains to you why I'm not making simple tweaks to modifying infantry combat. My view on the game and fiction is that they go hand-in-hand, and that this whole thing is supposed to be in the future.
Anyway, this is where my idea for alternate infantry types comes in. Part of it stems from looking at unarmored infantry with heavy armor and my dislike for point counting. (See my demolition attempt rules as an example of what I prefer.) Another part of it stems from the idea that the standard infantry of BT (BMR or TW) are the best equipped, the best trained, and the best in shape and highly motivated.
I'm thinking that 'standard infantry', with their uber equipment will get a second roll on the cluster chart indicated for the 'actual damage' AC result. IE, you roll for an AC 5 or 10 or whatever as above, but then use the result as the new column to roll under for the actual damage. This is only done for 'standard' infantry which are in cover of some sort.
Then, we can introduce other types of infantry to represent the not-so-elite and the ill-equipped.
I'm thinking of calling them 'Normal' and 'Irregular' types. At some point, I'm going to start looking into range boosts against these sub-standard types, as well as changes in damage effects.
Although, as somebody else pointed out, somewhere - if not this thread -, that infantry of such lower calibers should be working on a completely different scale. I agree with this. Taking this approach would allow for sub-par vehicles which don't rate even as a lowly support vehicle, but giving them some sort of effect against that which they were designed to fight - men, and like vehicles.
I'm still open to comments and suggestions and questions. This has actually been rather helpful.
