In this review, we take a look at the Legiones Astartes Special Weapons & Heavy Weapons (Missile Launchers & Heavy Bolters) upgrade sets, also available for pre-order since yesterday. Both plastic kits contain special and heavy weapons to upgrade the new MkVI Corvus armour Space Marines to Legion Support and Heavy Support Squads. But are they also compatible with the older MkIII and MkIV Legionaries? Here you will find the answer.

Legiones Astartes Special & Heavy Weapon Sets Review
These items were kindly provided by Games Workshop. Thoughts and opinions are our own.

Both weapon sets will be open for pre-order from 4 June 2022 and will be released two weeks later on 18 June. The RRP will be £26 / 34 € / $42 for each set, with discounts available at our partners Wayland Games, Element Games, and Taschengelddieb. The Legiones Astartes Special Weapons Upgrade Set contains 60 special weapons, the Legiones Astartes Heavy Weapons Upgrade Set (Missile Launchers and Heavy Bolters) 10 each, as well as arm pairs for the shoulder-mounted Missile Launcher.

On the Horus Heresy Open Day, two further sets were announced, one with 10 plasma cannons, 10 heavy flamers, and 10 multi-meltas, the other with 10 volkite culverins, 10 lascannons, and 10 autocannons. A release date for these is not yet known.

Legiones Astartes Special Weapons Upgrade Set review

The Special Weapons set contains two identical sprues, each with 5 flamers, plasma guns, meltaguns, rotor cannons, volkite chargers, and volkite calivers. Grav guns are unfortunately not included. Each of the 5 weapons fits exactly to one of the five different arm pairs from the new MkVI kit, so you have to be careful when assembling and read the instructions carefully. I’ve put the assembly guide below:

The question is: do the new weapons also fit the old models? Not really. The MkIII and MkIV kits have the left hand modelled on the left arm, whereas the upgrade sets and the new MkVI Marines have the left hand modelled on the weapons. So to make the weapons fit the old models you have to remove the hands from the left arms, which is not so easy as the MkIII and MkIV bracers often overlap the wrists.

Horus Heresy Special Weapons Upgrade Set Compatibility

Also, the MkVI models’ arm proportions seem to be slightly different. As you can see on my MkIV test model, there is a big gap on the right wrist that needs to be filled with Green Stuff.

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Horus Heresy Special Weapons Upgrade Set Review

And how about removing the left hand from the guns? Well, you’d still have a gap on the right wrist. And the way they sculpted the thumbs resting on the weapons makes it hard to remove the hands without damaging the details of the gun.

So, it’s not impossible, but making these fit requires a lot of work. Why they changed the design of the hands and arms of the MkVI models is beyond me. They could have just kept the old layout, thus ensuring cross-compatibility, but no.

Legiones Astartes Heavy Weapons Upgrade Set (Missile Launchers and Heavy Bolters) review

This set contains a total of four sprues: The first sprue contains 5 Missile Launchers and 5 Heavy Bolters, and is included twice. The second sprue contains MkVI arm pairs for the shoulder-mounted heavy weapons and two augury scanners, and is also included twice. This sprue will no doubt also be used in the two other Heavy Weapon sets that have been announced.

Legiones Astartes Heavy Weapon Upgrade Set Sprues

As with the special weapons, the weapons are matched to the 5 distinct arm pairs/poses of the MkVI kit, but as the shoulder-mounted missile launchers come with their own set of arms, they should be compatible with any of the 5 bodies.

Only MkVI arms are included for the shoulder-mounted weapons. For MkIV models, this might still work, but compared to the heavy MkIII armour the difference is too obvious. It’s a pity they didn’t consider the old kits for this set either. However, MkVI arms are very similar to MkVII arms, so the missile launchers also fit well with Firstborn Space Marines.


I’m torn when it comes to assessing the value. Of course, it’s cool to no longer have to rely on expensive resin weapon sets. But I’ll be honest, I would have preferred a lower price. Of course, the upgrade sets are significantly cheaper than Forge World’s weapon sets, and you get a lot of weapons in each set, even if the special backpacks have been rationalised away. But since most armies won’t field more than 1 or 2 support and/or heavy support squads, a lot of plastic will remain left unused. It seems like a good idea to share the upgrade sets with friends from your gaming group.

There is one good thing about the sets, however, and that is that they will also be available from independent retailers. Our partners Wayland Games, Element Games, and Taschengelddieb offer up to 20% savings off the RRP:

If you use our links, you’ll be supporting our work at no extra cost to you, a thousand thanks for that!

More Horus Heresy content is on its way – check back later this week, there’ll be more reviews, and tutorials for Imperial Fists and Sons of Horus, which you can see above. Let me know what you think about the new upgrade sets in the comments below, cheers!


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  • Lots of weapons in a box
  • Plastic, not resin
  • Available from independent retailers


  • Have been designed for the new MkVI models only
  • MkIII and MkIV models require lots of conversion work
  • No special backpacks for the heavy weapons

Final Verdict

Actually, the upgrade sets are a pretty good idea. But the fact that the weapons only fit the older MkIII and MkIV models with great difficulty, as well as the rather high price, dampen the joy. At least the Special & Heavy Weapon Upgrade sets are considerably cheaper than the resin weapon sets from Forge World, and they are also available from independent retailers, which makes them much more accessible.