HH special and heavy weapons on other firstborn marines

[roryokane]

Quick question, chaps.

 

I’ve got some extra heavy and special weapons (complete with arms!) from the heresy kits, and some firstborn marines with no weapons. I know the arms aren’t cross compatible (hands on weapons vs not on the old arms), but do the kits fit wholesale onto say, Mk IV or 40k tactical squad bodies?

By fit, I mean without lots of chopping or without using lots of green stuff.

 

I had a quick squizz with the search function and more broadly and couldn’t find an answer. 

Would like to add some old-style HH weapons for variety to the classic 40k Mk VI/VII/VIII tactical models (and the Mk IVs too, I suppose!), but wanted to see if it was feasible without too much work!

[Firedrake Cordova]

Tale of Painter's review has some pointers - don't know if that's any help?

[LameBeard]

I added the new mk vi beaky arms to the old mk iv Maximus bodies with very little  issue. True I was giving them bolters, but I don’t think special weapons would be a lot different. I plan on adding a heavy flamer and a Volkite Culverin I got from a bits store in the same way. 

Now I dug these out thinking they were finished but I see they need eye lenses doing and decals matted down - so back to work!

 

I don’t think I needed green stuff (shoulder pads cover it), but a little bit of ‘give’ at each joint might be required, I’m not convinced the mk vi flat areas at each shoulder are completely parallel as they are in the firstborn kits.

Edited January 17 by LameBeard
Pictures

[Sky Potato]

I put some of the MkVI arms and special weapons onto MkIV bodies.

 

Some of the pairs of arms were not a 100% flush fit, but there was enough contact area between the arms and body for a stable glue joint, and any slight gaps between arms and body were covered completely with shoulder pads.

[roryokane]

On 1/17/2025 at 12:11 PM, Firedrake Cordova said:

Tale of Painter's review has some pointers - don't know if that's any help?

Sadly no, as it doesn’t consider using the arms provided (I.e. using the Mk VI arms) with older torsos, and has the same thing about the hands being attached to the weapons etc that others do.

 

I want to know if the arms and weapons combined as intended for use on new Mk III/VI torsos can be used on older torsos.

[Grotsmasha]

Typically speaking the mkIII and mkVl torsos are marginally wider, somewhere between 1/2mm and 1mm. The arms from the newer plastics will glue onto the Firstborn / mkIV torsos just fine , but it won't be a 100% flush fit. Some 0.5mm plasticard between the shoulder and torso on just one side will make up for the gap and give you that flush fit. A single small, 6mm round disk will do it and it won't look out of place, just another piece of undersuit ribbing.

 

Edited January 19 by Grotsmasha

[Sky Potato]

The MkVI torsos being 1mm wider than the older MkIV would completely account for the arms not fitting flush. Good shout with the plasticard spacer, that’s worth remembering.

[TheArtilleryman]

They fit just fine. Here’s some MK IV with heavy bolters and some with volkite calivers (same scale marines as firstborn, when they were still cross-compatible):

 

All are using the new MKVI arms and weapons, while everything else is the old style space marine kit. Weirdly, I didn’t notice any issues with the size of the torso and to my eyes they fitted fine without having to add anything else.

Edited January 19 by TheArtilleryman

[Grotsmasha]

11 minutes ago, TheArtilleryman said:

Weirdly, I didn’t notice any issues with the size of the torso

 

It's not every kit, but some, typically two handed weapons can't slide far enough together, usually due to magazines, and can cause the support arm to angle out slightly.

[Sky Potato]

7 hours ago, Grotsmasha said:

 

It's not every kit, but some, typically two handed weapons can't slide far enough together, usually due to magazines, and can cause the support arm to angle out slightly.

Exactly this. Some of the matched pairs of arms fit better on the MkIV torsos than others.

 

If I was paying more attention, I probably should have recorded which pairs were better fits. I will if I do it again.

[roryokane]

11 hours ago, TheArtilleryman said:

They fit just fine. Here’s some MK IV with heavy bolters and some with volkite calivers (same scale marines as firstborn, when they were still cross-compatible):

 

All are using the new MKVI arms and weapons, while everything else is the old style space marine kit. Weirdly, I didn’t notice any issues with the size of the torso and to my eyes they fitted fine without having to add anything else.

Do the shoulder-mounted heavy weapons fit okay with the nozzles of the backpack?

[Grotsmasha]

1 hour ago, roryokane said:

Do the shoulder-mounted heavy weapons fit okay with the nozzles of the backpack?

No, they won't if in the raised position. IIRC, the HH kits came with packs with the nozzle missing on that side, so it wouldn't be world-breaking if you simply clipped the nozzle from that side off.

[TheArtilleryman]

3 hours ago, roryokane said:

Do the shoulder-mounted heavy weapons fit okay with the nozzles of the backpack?

I haven’t tried as I don’t have any, but as @Grotsmasha says, you’d need to clip one of the backpack exhausts off to make them fit. I had to do this with my Forge World Lascannon guys anyway.

[LameBeard]

Mk IV Maximus kit comes with a missile launcher with special “one vent only” power pack - so yes, @Grotsmasha is right there is precedent for shoulder-mounted weapons missing the vent this side.

[roryokane]

On 1/19/2025 at 9:34 PM, Grotsmasha said:

No, they won't if in the raised position. IIRC, the HH kits came with packs with the nozzle missing on that side, so it wouldn't be world-breaking if you simply clipped the nozzle from that side off.

So that's true of the Mk IV Missile launchers.. It doesn't look like there are special backpacks for the Mk III/VI shoulder-mounted heavy weapons. Hence my asking. try it and see what happens time, I guess!

 

22 hours ago, TheArtilleryman said:

I haven’t tried as I don’t have any, but as @Grotsmasha says, you’d need to clip one of the backpack exhausts off to make them fit. I had to do this with my Forge World Lascannon guys anyway.

Ah, I think I managed to snag a single "legion heavy weapons" blister that had the shoulder-mounted ones from ebay.

I'll have a play the next time I get a chance to do some serious hobby work!

[Moonstalker]

My Lascannon/Autocannon/Volkite kit did not come with backpacks missing a side vent.  I have so far only used these to convert Primaris marines but I have plans to put some autocannons on firstborn for a Long Fang Squad (count-as missile launchers, probably).

 

I had to make an instruction manual as an assignment for a technical writing class I was taking, so I have documentation of how the Primaris conversion went.  I don't know how helpful it will be for you, but I have attached it below.  With the lascannon-armed marines I had to cut the arms and add spacers, and the fit is still a little bit fudged.  However, I did a squad with volkites that was much more straightforward - I used the bolt rifle arms from the intercessor kit with the volkites.  I had to trim a bit around the right wrists to get them to fit and if you really cared about it the hands on the gun look a little small for the size of the arms, but the fit for those was otherwise excellent and easy.

instructions-project-final.pdf

[Cadmus Tyro]

I used the new MKVI Lascannons on some old MKiii torsos, they seemed to work ok from what I remember. I used a mixed armour approach with MKIV packs and MKIV destroyer helmets: 

 

Spoiler

 

[Jukkiz]

After rummaging through my folder, i managed to find pic of original Heavy weapons options set from Forgeworld, with backwards mounted backpack heat vents

[TheArtilleryman]

1 hour ago, Jukkiz said:

After rummaging through my folder, i managed to find pic of original Heavy weapons options set from Forgeworld, with backwards mounted backpack heat vents

So that’s what those backpacks are for… I have a bunch of Forge World heresy stuff that was in a big eBay job lot and I wondered why there were those kind of backpacks.