But the Banshee can fire it's AC for 30 turns.
I know, I like it too. :) But it needs a lancemate to help crit-seek for it.
Because that's the way BattleTech is. Obsoleteness gives way to progress. X-Pulse lasers are totally superior to Pulse Lasers. PPCs are almost obsolete when theres 3 stripes of new PPCs to suit different needs. Heck, RetroTech was completely discarded even in the tech-poor Succession Wars. So it's not that big a leap for LBXs to supplant ACs just as ACs supplanted Rifles.
Yet Retrotech was needed even -after- the Succession Wars thanks to demand when the Word decided to throw down. Necessity is the mother of creation, not time.
(Also, I contest that X-pulse Lasers are not superior to Pulse Lasers in that the increased range being traded off for heat greatly reduces the amount of firepower a unit can project in one round; it's especially apparent on vehicles, where they're limited by Heat Sinks in construction rules, as well as faster 'Mechs [for which range is less important] that rely on Medium Pulse Laser-boating, like the
Nightsky or recent
Ostsols.)
And speaking from an out-of-universe perspective, weren't RetroTech units and Rifles created -after- the standard technology in the Inner Sphere was established and given fluff? It appears there was a desire to create so-called "obsolete" equipment for the enjoyment of players even as the technology level of the Sphere went through the roof. Some people apparently like fighting with rusty pitchforks, man!
Actually due to their large crit size and the way special munition ammo rules reduce the amount work, it isn't actually that beneficial for assaults to carry them. But then assaults have always been units that favoured mixing the ballistic and energy weapons together. Because they have the free tonnage, just not the crit space.
However when it comes to lighter weight mechs that can usually only afford one big weapon system, the autocannon has always lacked behind due to their heavy weight, large size, ammo dependence and in the case of earlier eras. The class 10 and 20 still generate noticeable heat.
Once you get double heatsinks the Heavy PPC pretty much becomes the one weapon you will stick on everything if you can't mount a Gauss Rifle. At 10 tons a lot of mechs can carry it, at 15 heat every mech can tax it as their primary weapon. Being ammo independent and capable of headcapping it just blows the class 10 autocannons out of the water. The class 20s are too heavy to compete. And the 5s and 2s just do too little damage for their weight to even be worth it as a main weapon.
(That is why I see the LRM as the main weapon on the Garm and the LB-5-X as a backup and crit seeker/AA gun.)
Inner Sphere Double Heat Sinks are a big deal when you try to energy-boat with an assault 'Mech, because often a lot of them will be outside of the engine taking up 3 crits apiece, which can really add up. And that's why Gauss Rifles are okay to use on them!
Right, I didn't mention 'Mechs lighter than 80 tons for a reason...the weight game is completely different once you have to worry about all the other stuff a 'Mech can do in design. Still, it doesn't stop TPTB from sticking Rotary AC/2s on
Wolverines!
I'd advise against the overuse of Heavy PPCs, though--there are 'Mech-hunter 'Mechs out there designed to chase skirmishers down and get within minimum HPPC or missile range, throttling them with Pulse Lasers and melee weapons.
