Originally Posted by ThoseKrazyKasrkin
Hwts cannot overwatch as they are heavy.
BUT they have a lasgun : )
Rubbish- heavy weapons can overwatch... blast weapons can't (so no mortar or frag missile overwatch, everything else is golden).
Lascannons- very expensive and very easily killed. Good way to get lascannons into your army, but too fragile for their cost for my liking. I would probably use them in infantry squads (or defensive vet squads) rather then heavies...
Mortars- cheap, effective, lovely. I'm a big fan of mortars, especially effective for heavy squads as you can just hide them behind terrain so aren't as vulnerable as other types of weapons team.
Autocannon- excellent all-rounder and quite cheap. I also think its one of the fluffiest weapons to give your IG. I use autocannons in defensive infantry squads to give some extra beef to their shooting (especially if I blob up and then use Bring It Down... very nasty).
Heavy Bolter- don't bother, just take the autocannon. Against infantry the HB is only marginally better then the autocannon (and mortars would often be better) while against vehicles the autocannon is miles ahead.
Missile Launcher- another excellent all-rounder. Great against most MCs, good against tanks and able to rip nice large holes in hordes (or instant death MEQs with no save). I run a couple of heavy units with missiles and while they let you down against heavy tanks they do smash transports and light tanks around (although at times you would wish for the AP2 of the lascannon).
Personally I don't like the vulnerability of heavy weapons squads.... but you can't deny that they are very useful since while they may be easy to kill they are also effective ways to get large numbers of heavy weapons into your army that can be ordered around (vendetta may be better, but I think its far too good to use). First and foremost though I think you should have a plan for infantry/vet units and upgrade any that aren't intended to be moving forward with heavy weapons: they are the best place for heavy weapons since you have a whole load of spods to die first and protect your weapon (and remember you can move with everyone but the heavy weapon and still fire at full effectiveness). Only after that would I go for heavy squads (except for mortars- they are only really useful in heavy squads, but being able to hide them is a huge bonus to survivability anyway).