OK, so you can’t have heavy weapons in guard squads any more. This likely means that if you had a guard army prior to the 10th edition Astra Militarum codex, you now have a bunch of spare big guns to form into dedicated units. Here’s some ramblings on how you might do that.
I've written about this topic before, during the index era when there was only one type of heavy weapon team, and they cost a bargain basement 50 points for three. Under the codex we now have three variants, and following some patching-the-patch shenanigans, cost 65 -75 each. This means its possible, if not especially wise, to spam 27 heavy weapons for 615 points. The specifics of each variant is something I will discuss below, but their basic functions see a lot of overlap with each-other and the now retired Index version. The argument against Heavy Weapon Teams is the same as it always was: fragility. These units are directly comparable to 6 guardsmen in terms of durability, arguably worse as damage 2+ weapons have use against them, and only need to suffer two wounds to see a loss in output. Placing them in a transport for protection is also discouraged in the codex, as each base now uses two firing port slots, which would be annoying if the idea of two of these poking these out of the top of a Chimera wasn't a frankly daft mental image. Previously, this dynamic favoured the Infantry Squad, which could protect those same weapons with numerous ablative wounds, but that unit no-longer exists. The argument for heavy weapon teams is now their density and availability of firepower at the infantry scale, and the potential to force dilemmas by their presence. If you need more of a specific kind of dakka in a list, this is likely the cheapest way to do it, and its very easy to get Orders for them. Take Aim! is so obviously a gimme I nearly forgot to mention it. Heavy weapon teams obviously do well in the more infantry centric detachments like Siege Regiment (Incendiary), Bridgehead Assault (reroll 1s) and Recon Element (Cover bonus), although Combined Arms is awkward as its it creates a nombo-combo. At the risk of spoiling the article, the overall balance between the three options is to place Catachans first, Krieg second, and Cadia last, but there's there's not much in it. At time of writing, a change of 5 points in either direction could totally rearrange that pecking order. The current price of 65+ also seems rather high due to, again, the durability issue. An opponent would have to wiff pretty hard not to wipe out one of these on the first attempt, and if you're honestly scared of mortars I want to know who hurt you.
Let me start breaking down the specifics. Cadian and Catachan heavy weapon units are very similar, and this will likely remain the case until such time as the latter gets a range refresh. They have the same basic statline, that same habit of dying to any amount of direct attention, and the same weapon options. There is a somewhat incidental difference, in that Catachans have lasguns as secondary weapons rather than laspistols, and can thus fire those weapons along their big guns, but I feel thats an edge case. The difference comes from their special rules, Cadians being rather niche, and Catachans having two rules likely to be useful in every game. Cadians get the rule from the Index HWTs, they are that unit reskinned, and thus get a buff when using the Fire Overwatch stratagem. As this scales up to a 4+ to hit when a Platoon unit is close, it looks useful on first impression, but in the wider context it's hard to get use of. The Catachans meanwhile have a Scout move, and a reroll 1s ability against vehicles/monsters. The Scout move is great as mobility wins games, you can use them as screens if need be, and Bring it Down! just makes them better with a majority of the things you'd want heavy weapons for, although obviously not all targets. Oh, and it does work in Overwatch too. So, assuming points costs remain comparable, and in the absence of other factors, you'll be taking Catachans over Cadians almost every time. Or you'd take Cadians as you'd maxed out on the Space Australians.
Now, there is a temptation at this point to break down each heavy weapon and what they do. Practically however, there's two main options, and a number of niche tools you would likely decide against. That's how it goes with 10th ed units; in the absence of granular points costs, you are doing well if there's two workable choices. With heavy weapon teams, those choices are the lascannon, the anti-tank option and the mortar, providing light artillery. Neither of these options are necessarily spectacular at what they do, but they do offer capabilities otherwise lacking in Guard infantry. I acknowledge that there are usage cases for autocannons and heavy bolters for either Cadians or Catachans, mainly in the context of the Combined Arms detachment, but they are fairly niche. Missile Launchers need a complete revamp though. The lascannon makes it possible to significantly damage, and occasionally destroy outright, a tank at 48 inch range. Mortars are much less damaging weapons by comparison, you're looking at a lot of inaccurate strength 5 shots with the benefit of cover, but it allows you to sidestep the durability of such units through indirect fire. Please note: neither plays nice with Born Soldiers, that’s why I was down on Combined Regiment above. You take the lascannons to add more anti-tank, and to force dilemmas onto your foe. You take the mortars to annoy your foe with weak attacks they can't hide from. Lascannons are the active choice, a foe has to respond if their force has tanks and such in it. Mortars let you do passive things like screen out your deployment zone as they don't need a good firing position. Neither the Cadian or Catachan options really benefit the mortar, not really. You could try mortaring a tank with the Catachans, in that you do get reroll ones, but you'd be at that all day. Cadians are even less suited, as indirect attacks don't work with their Overwatch ability, and mortars make it far less likely they'll be placed to use it anyway. The Lascannons? Well, Catachans are the unambiguous winners there, although the Cadians could get to use their ability with them.
Krieg Heavy Weapon Teams, meanwhile are different. Almost so different they could be an article by themselves, but the contrast between them and the above is important to make. With respects to the more subtle differences, these teams have a slightly better save, worse movement, and a forth member whom enables their party piece while he is present. There's a few edge cases where this matters, they do get up to a 3+ save in cover for example but its something easily glossed over. The practical differences come from their weapon choice, and their fire on death mechanic. Kriegers have no indirect fire option, they have actual artillery elsewhere, so by default they can't avoid taking casualties. However when they do, and this is another dilemma for your foe, they have a 50/50 chance of shooting in revenge. Consider this to be akin to a posthumous Fire Overwatch; its not something you can control, but it otherwise functions as a regular ranged attack in the enemy turn. Orders do apply, it doesn't work in melee, but you don't have to target the murderer. The complications for you as the player is that these Krieg teams are a touch too expensive to be truly disposable, and then there's the weapons. Krieg teams have access to the basic lascannon, and rank behind the Catachan option as they aren't notably good with them. Its much harder for a foe to stop them from firing of course, which is handy, but for direct fire purposes, you're paying more for the same gun. The other two options are where it gets complicated. The heavy flamer option is very much THE unique selling point, rivalling the Hellhound tank, and quite capable of killing 4 or 5 marines outright in a single roasting. There is no direct equivalent, but the range of 18 makes it tricky to use. Its an ambush unit, not a fire support unit, so you'd need to keep it safe until it can be useful, whereupon it becomes an unholy terror. Burn on your turn, burn on Overwatch, then burn in death. That's not something a foe lets happen twice. Or once if they are actually paying attention. So they need transports or placing in reserve, unlike every other variation discussed here. The heavy stubber option meanwhile, seems to be made for a metagame that doesn't exist, as thematic as it is. While that weapon is great at killing chaff units at long range, that’s not something you usually need. There is a fascinating comparison to make with heavy bolters though.
Conclusions? Well, like I said, its probably Catachans first, Krieg second, and Cadians third. Catachans are just generally good on their own terms, and when running Jungle Fighter themed list. Krieg are much less flexible, but have some interesting gimmics that make them worthy of consideration. Cadians are painfully generic by comparison, but force no strong preference on the player and do the job. All have the life expectancy of a wet paper bag in a thunder storm, which places some limitations on their use. In big picture terms, there’s not that much between them however. So field them however you please, but I’d recommend the Catachans option in the absence of a specific need or preference.
Watch ‘em get nerfed in the next balance patch...
