As I stated before (not in these words, obviously), I'm with Weirdo on this one.
Current firearms have been given stats as the "vintage" weapons in the Companion, and they're significantly weaker than their 31st century counterparts.
I explicitly said my interpretation of the extended ranges of auto-rifles and other primary weapons when paired with longer ranged secondary weapons was down to sharing improved targeting information. If you look at any of the faction armor kits, you see they all have relatively sophisticated communications built into their helmets, and more than one picture of them includes some kind of optical display (the one that springs immediately to mind was one of the old Lyran pictures). It's a small step from this kind of information extending effective range to enabling effective damage to extremely complex machines with plenty of joints and other weak spots.
I would be perfectly okay with that if that was something explicitly talked about in the infantryman's kit make-up. It suggests something else that isn't talked about - smart/homing rounds. But, point me to a page in any book describing infantry kit - do they have homing rounds for their front line infantry? Certainly would have been a great starting point for precision AC rounds, don't you think?
But, if that's the case, then the older BMR application of infantry damage as one large grouping or 5-point clusters would make more sense than the purely rules-bound for BAR sake 2-point clusters.
And, this also is forgetting something we seem to often forget as well, Mechs (and other armored units, but especially Mechs) are constantly moving, aren't really the plodding 'stompy' robots that people talk about them as. It's hard to target the 'weak' knee joint while it's on a pumping limb that doesn't seem to stop except for intermittent breaks in movement for whatever reason. And, I haven't even gotten into the supposition that there might be some sort of defensive algorithm or program that helps the Mech detect incoming shots, where they'll probably land, and turn a glancing, better protected face into that attack, thus letting the armor deflect the energies like it's designed to do.
And, lets not forget the ambient ECM that all war machines and units are putting up to make such targeted attacks difficult.
See, the real problem that we're facing is that nobody in charge has bravened up to actually come up with some final guidelines on how to interpret how advanced the BT setting is. The rules are schizophrenic when it comes to infantry and armor and their interaction with Mechs and buildings because there's no final word on how that should be reflected in the setting's gear, and how the settings gear should be reflected in even an abstract fashion for game rules.
The statement in Total Warfare that rules are rules, fiction is fiction, and art is art, is erroneous, or we wouldn't have people throwing fits over the placement of the Marauder's dorsal gun, the fact the Behemoth only has one, or the placement of the LRM Tube on the T-Bolt.
I certainly didn't, because I saw the placement as cosmetic, and that the bulk of the cannon for the Marauder probably simply extended into the right torso from the base of the gun, right where the ammo feed split away into the left torso. Or, some weapons, like the Atlas's hip-mounted LRM, are rapid-firing the appropriate number of missiles/beams. I had no problem with that, but later artists started adhering to the placement of the weapon on the table for a Mech being the deciding factor of the placement of the barrel opening on the picture. So, they certainly did.
I have no problem imagining that infantry weapons - specifically those armed for front line engagements with advanced armored units like Mechs - are able to fire rounds to sandblast away at the armor. There's special gear required for that though, and most likely training, as well. A level of coordination that you don't get with green troops. And, combat losses would hamper that unit ever getting very far. I have no problem with the notion that support weapons could increase the effective reach of said weapons by acting as a homing corridor, or weakening the armor enough that the hits have better chances of scoring damage.
But, the problem lies, then, in the fictional depiction of infantry, if that's the case. And, there still needs to be some tweaking with the rules, because that at least suggests the support weapons should be capable of great damage on their own, and not merely supplementation to the hailstorm.
And, if people have a hard time with that, and insist on infantry light weaponry not being very effective against futuristic armor, which I can also get behind, and that the fictional depiction of infantry kit is what we should adhere to, then the rules have to change.
I'm actually kind of fond of the 3rd option - that both are true. That the typical infantryman we've seen depicted in BT is the large rank and file, but what we see on the board is something outside that depiction, something truly special.
And, I'm with all the people having issues with the way Mechanized Infantry works. That's too big a disconnect, too abstract.