Hey guys. I wanted to talk a bit about Heavy Weapons today.
Since the new Codex, there's been a lot of talk about what Heavy Weapons to take, which are better, etc. I'm going to try and break the choices down for you, give you the reason for each ranking, and talk about how to maximize their effectiveness.
In my opinion, here's the ranking of each HW, based on effectiveness.
1. Missile Launcher
2. Heavy Bolter
Missile Launcher: This should be one of the staples of your line. It's a good, cheap, all purpose AT weapon, and can crunch MEQs quite nicely. It also has the ability to fire a Frag Template, meaning you can use it as an Anti-Infantry weapon if you need to, which is why it noses out the Heavy Bolter for the top spot. There ares ome problems, though. It does struggle with AV 13, and it can only glance AV 14 at best. Thos Frag Rounds I mentioned can kill infantry, but they're not the best at it, and should only be used in that role if there are no other targets, or you NEED to kill an infantry squad. Also, with only 1 shot per round, it's susceptible to the Guard's BS 3.
Tips for effective use: Always try to put these guys in an HW section, instead of in squads. It does make them a little more vulnerable, but you put three shots into the target in a single volley. That means you don't have to waste the shooting of three infantry squads, and it helps to balance out the BS 3. Also, combined with the "Bring it Down!" order, you can make them Twin Linked, which means you'll get at least 2 hits, if not all 3. Also, remember that Missile Launchers are good against top and side armour. Taking two sections, and placing them on both flanks, especially high up, means the enemy will be hard pressed to deny you a shot at the side armour of his tanks.
Heavy Bolter: If you want infantry dead, take the Heavy Bolter. It's got decent strength, good AP, and puts out a lot of shots. It's also cheap as hell. It can rough up Trukks and light vehicles, but you really should be using it to kill enemy squads. It's perfect for fighting IG, Nids, Orks, Tau, and can even make MEQs sweat, due to the sheer number of armour saves. The Str 5 does hurt it a little against Orks and MEQs, and can't do jack against heavy vehicles, though.
Tips for effective use: This is the perfect weapon for basic infantry squads, since they excel at anit infantry (if you're using your basic infantry with Plasma or Meltas, you're making a mistake, and we need to talk). HBs will magnify their squad killing power, and those 3 shots go a long way toward canceling out the BS 3. Issuing "FRF, SRF" or "Fire on my target!" to the squad makes them even better, as they can slaughter a whole enemy squad in a single volley. Don't bother using HBs against any armour though. MLs are better at it.
Autocannons: I'm going to catch some flak for saying this, but Autocannons are simply not as useful as HBs. They do fine against high toughness enemies, like the bigger Nids, and can slaughter Rhinos and other APCs, but they don't do as well against basic infantry compared to the HB, because they put out less shots (Remember, BS 3 means you'll only get 1 hit on average), and they don't do well against medium and heavy vehicles, simply because they need a 6 to penetrate AV 12 and glance AV 13.
Tips for effective use: Take Autocannons when you know you'll be facing light vehicles, or small groups of high Toughness enemies, like Tyranid Warriors. Always take them in an HW Squad, too. Since you're only hitting half the time, you can still put a decent amount of shots on the target, guaranteeing at least 1 wound or penetrating hit. Also, Vets with 3 Grenade Launchers and an Autocannon are great for ripping apart high Toughness targets, but never take more then one squad of them (or it would be too expensive). "Bring it Down!" and "Fire on my Target" are both good when used with AC Sections.
Lascannons: These are okay for dealing with heavy and medium armour and killing really tough targets, like Monstrous Creatures. That said, they're much more expensive than the Missile Launcher, and you only gain +1 to Strength and AP. They still have a hard time dealing with AV 14, so they can't always cope with Russes and Land Raiders (in fact, giving an SW Squad 3 Demo charges is cheaper, and you have a better chance of killing the target). They also have only one shot. While this is a minor annoyance for the Missile Launcher, it's a real pain for the LC, considering what you're paying for it.
Tips for effective use: Take them in an HW Section, and only take section in the army. A Vanquisher is actually a better choice for killing Land Raiders and Russes, but an additional Lascannon section never hurts. Have them hit side armour wherever possible, and use them to snipe the toughest targets facing you. Some people also like to use them for hunting Termies, but Meltas and Plasma are better for that, simply because they're more mobile.
Mortars: These are the problem children of the HW family. You need to take a lot of them for them to be effective, they have low Strength and AP, and are fairly inaccurate. They do use the Barrage rule, which helps, and are good against tightly grouped IG and Nids, since they deny them a cover save, and force them to rely on a 5+ armour save. They're decent against Orks, but against Tau (who will get a 4+ save from their armour even if they lose a cover save) and MEQs (3+ save), they're pretty worthless.
Tips for effective use: Take two HW sections, and hide them. Use them to hit gunlines or mobs of fragile units.
There you go. I plan on covering Special Weapons soon, too.