Actually, IIRC it was a niche in the rules that one of the rifle sets were more effective against BA than others. I cannot remember the specifics, but perhaps someone can.
I was just checking the rules, and for the rifles, the -3 damage IS an issue, I was thinking something along the lines of campaign use. Sort of, oh look, you have a shortage of funds and you need to replace some weapons type of thing.
I keep tossing around the idea of a Scorpion tank equipped with a heavy rifle for dirtbag periphery groups. In my mind, it's ideal because it gives you a tiny boost in damage against hard targets and a major boost against softer targets. Sure, you only have six shots, but it's a Scorpion. One way or another, that's probably enough.
Battletech transport rules take a very feline approach to moving troops in a combat zone: If they fits, they ships.
Rifles can be used as towed field guns... >:D
So does anyone use these?
I have repeatedly installed binary lasers on PC's 'Mechs when I run 3025-ish campaigns, and the players end up hating them. Once, the 'Mech never hit anything with the binary laser - quirk of the dice - in repeated sessions, while in the other case it was loaded on a 'Mech with severe heat problems so that binary laser was always idled in favor of the 'Mech's other weapons. The players are now convinced it stinks, though the problems had nothing to do with the blazer.