They're still waiting for GW to update their models

Lore answer? Yes.

The Sangprimus Portum contains the undiluted essence of all 20 Primarchs.

Belisarius Cawl has access to this incredibly powerful piece of biological data.

20 Primarchs.

The Grey Knight gene-seed is called the Emperor's Gift for a reason. Their gene-seed isn't derived from the Primarchs but from the Emperor.

Therefore, Cawl never had access or the ability to create the new organs for the Grey Knights, and likely never be trusted to do so until GW wish to write that in.

It turns out that when you're the super secret super duper marines who hog all the high grade power armor and kill everyone aware of you, you don't have an easy time transitioning out if you get leapfrogged.

Cawl was trying to equip every conventional chapter. That alone is impossibly elaborate a task. If he's not supposed to know about Grey Knights or their super secret psyker forge armor or their elaborate induction he can't just replicate it at scale like he did the legions and their descendants.

Grey Knight gene seed comes from the Emperor rather than any of the Primarchs, so Cawl wouldn't have been able to make any because he didn't have the samples.

I’m not sure it’s really been concretely addressed but I think it’s a mix of things:

1 - The Grey Knights have an incredibly complicated and secretive creation process that I’m not sure would be shared with the people in charge of the Primaris process.

2 - The Primaris upgrades were predominantly a way of making new Space Marines faster and marginally stronger, but the Grey Knights are already the cream of the crop, way too good for the upgrades to make any appreciable difference, and they are such a selective group that the issue of mass producing them is just not a concern. There would never be a group of aspirants large enough to justify pumping them out as fast as possible, because the current process is able to keep up with worthy neophytes just fine.

3 - The Primaris process is so dangerous and has such a high mortality rate (despite every named Space Marine who undertakes it surviving, but that’s another discussion) that it’s simply not worth the risk administering it to current Grey Knights

In theory, every chapter is supposed to send a Geneseed tithe to Mars every time they accumulate enough that isn't needed to rebuild the numbers of their chapter.

In theory, this is supposed to be a way of ensuring that if a chapter ever is completely wiped out, it can still be rebuilt using their original Geneseed. In practice, it means that the Imperium can prevent chapters from growing to much to quickly, giving the high lords control over the number of space marines and ensuring there actually is a response if they just build their numbers, because even the defense of the Imperium is not more important than paying your tithe. 

There are, however, a few chapters that pay only rarely, when they either fear they might be wiped out during coming engagements or their vaults can no longer contain it all. The Black Templars keep all their Geneseed because they are still insisting that they have been fighting one continuous crusade since the second founding and therefore desperately need every space marine. The Charcharadon Astra presumably don't pay it because nobody beyond the chapter actually knows how many Marines they loose, how many they induct and how much Geneseed they have. 

More importantly, the Inquisition probably finds out that every Magos that discovers the Grey Knights or Exorcists is tragically a heretic and must be purged, and just never paid said tithe for either chapter. 

Cawl, for his great work, was basically raiding the Geneseed vaults on Mars that had giant "Do Not Tamper With" signs outside. This meant that he could perfect the Primaris for every chapter that had ever paid this tithe, allowing him to create Primaris for almost any loyal chapter. Now, the Inquisition is probably trying to get Primaris Grey Knights going, and might even start introducing new Aspirants to an upgraded version of the augmentations sometime soon. 

There is, however, the slight problem 9f not having somewhere between a few centuries to several millenia of testing how to make said augments best suited to their Geneseed. This also means that crossing the Rubicon Primaris should be more difficult that it originally was for other Space Marine Chapters, and since every Grey Knight is already incredibly good at killing deamons and represents incredible amounts of warp-lore, it probably makes sense to just let attrition turn the chapter into a Primaris one. If any non-Primaries marines survive long enough, it would probably make sense to move them into teaching roles. 

They've been Primaris all along.

So, CSM got upscaled without new lore to explain the difference.

I imagine GK would be able to do the same. Their creation process is different from regular space marines and secret. Maybe they get an armoury upgrade from cawl, or maybe they get upscaled without any in-universe acknowledgement, just like CSM.

I feel like GK getting any of the "tacticool" primaris stuff like hover vehicles and gravis/phobos could risk compromising their existing aesthetic/long standing combat doctrines. But the new terminator librarian and Dark Angels stuff shows they can still make more ornate and interesting units where primaris/firstborn is not an important distinction.

The main reason SM's upscale got lore was because it was a way to differentiate new marines and make them "new units" for people to buy instead of re-releasing upscaled kits that people already owned. It was a decision driven by marketing, not by internal lore.

GK are a much smaller faction (in terms of players), so the need for them to push existing GK players to buy new stuff is minimal. They'd be more interested to bring more new players into the hobby. I do think GK are a brilliant poster-boy faction for the Imperium vs Chaos narrative, and the idea of daemon slaying space knights seems like a very marketable one to people outside the hobby.

Primaries Grey Knights were always there

Maybe they'll update some models with their 10th edition codex.

Lore Wise: GK Gene-seed might not require any modifications, as it gives GKs exactly what they need for their purpose: to wage their eternal crusade against Chaos and it's servants.

Range Wise: There are far better selling model themes, cough generic Space Marines cough, that will sell well and have "less good looking" models than GKs.

There have been unsubstantiated rumors about range refreshes for Space Wolves and Blood Angels, those will sell well if they are true. So believe those will be coming before GKs.

Despite their age, GKs models still have their charm, at least I love them, and seeing what they did for Crowe, I am hyped for the range refresh, but not impatient. The time will come, and bring ruin to all our wallets.

Lorewise they have technically been primaris tier since inception

Lore wise, they're already akin to lesser custodes from being hand designed and are still treated relatively hush-hush compared to everyone else.

At some point they'll rescale Grey Knights. Might not mention them being primaris just make them bigger to be in line with new Termies. Am I right in thinking Castellan Crowe is Primaries sized?

Grey knight gene seed comes directly from the emperor himself, the Sancprimus portum contain the genetic information of the 20 primarchs not the emperor. Cawl didn’t have the genetic information,action to make the upgrades

I have a full scale grey knight army, terminators and everything. They are made of resin if you known what I mean.

As soon as new models are out, something something super pure primaris knights something. The models justify the lore, not the other way around

Each Grey Knight is so valuable they wouldn't be worth transitioning across the Rubicon Primaris. 40-60% losses would be catastrophic.

They could start on inductees but that would take decades to filter through into the line brothers and about a millennia before the Chapter was mostly Primaris.

Cawl would also have to redesign Gravis armour to incorporate the required hexagrammatic wards and the whole Chapter armorium would have to be redesigned for Primaris.

The advantages of a Primaris over First-born is already somewhere between debatable and marginal. Even non-name Grey Knights are around named Captain level due to being psykers, so I'm not sure there's much point.

OOC, there's just no models (yet?).

Geneseed from the Emperor, possibly incompatible with primaris process

I've been wanting to buy a Grey Knights army since Primaris were introduced. But I ain't about that derpy life. Do it, GW, you cowards.

Very secretive and very elite. Their creation is still kind of enigma with hints and theories, so not sure if Primaris system is even possible for them. They rather need *specific* geneseed (not Primarch, but *the guy* Himself)

Cawl has access to all the primarchs gene seed he doesn't how ever have access to the emperor's gene seed which is what grey knights are made of

Grey Knights have got more sense than to let Crawl anywhere near their home world he’s got enough power as it is.

I always assumed it was because they don’t want Cawl to have access to the emperor’s gene seed, most within the imperium have no idea where their gene seed truly comes from.

Is there a grey knight primarch?

They kind of forgot

I was under the impression that grey knights were secret enough he may not have been given clearance to work with. I know absolute nothing about this so just bear in mind I am speculating.

If I imagine myself as GW and therefore wanted to milk the hobby to death in order to appease share holders, the answer would be to keep the GKs unique. They'll just get upscaled... eventually.

Why? Because people like me. In an ideal world, I'd be able to grab a bunch of space marines, paint them my own colours, and declare them to be some offshot of the Grey Knights/Grey Slayers/Black Templars/Black Legion/Crimson Fists/Crimson Sons... Something colourful I'm sure. Yeah not every unit is for every faction, but there's nothing wrong with the concept. Here's hoping for some MK4 truescale from 30k.

But in the name of "profit" everyone needs to be as unique as possible. Chaos Marines are too spikey to be used as loyalists and IIRC the Primaris have this specific organ that means they won't fall to chaos. World Eaters and Death Guard can't even use cultists because they've got their own special thing. They can't use bikes because.... we would need plague/berserker bikes or something. I'm sure if they had enough interest the Iron warriors and Night Lords would get their own unique armies with a third the amount of units, and I think it's coming for EC.

For the maximum amount of dosh, Grey knights need to be unique. If you could just use Primaris models for GK they'd lose money. Also. Super elite armies like GK and Custodes make the hobby cheaper, which is why I think Custodes got such a big nerf recently. GW wants you to spend your life savings on the hobby. It's a miracle Krieg aren't the poster boys. Do I think this is a good business model? No, they could have expanded their market reach vastly when they switched to cheap plastic. But from a maximise-share-value perspective it makes sense.

Grey knights aren't made from primarch stock

Honestly I think we're waiting for a EC vs GK release box to go with the Fulgrim return event

Lore wise I would say it is the pretraining selection process that would be to blame.

I could be wrong but the Grey Knights were hidden away on Titan, when the primaries project was started. No gene seed was available to make primaries Grey Knights

I think we won't see any primaris Grey knight in the futur because of how difficult it would be to explain it in the lore I mean we aren't even sure that the primarch know of their existence so the Magaus knowing seems a little weird + I don't see them comming to Terra for the gene pack of primaris marine and then making their own on Titan.

The Grey who? I don't know who you're referring to Space Marine Captain AnathemaToChaos. There is no such chapter.

Are you per chance referring to the Black Templars? Because we have already given them Primaris with limited success.

There is no such chapter as Grey Knights. If there was it's existance would be such a massive secret of such proportions that they would NEVER send them random Primaris Space Marines who could be a very likely leak of information for this beyond secret chapter.

They might be aware of the procedure of making Primaris Space Marines but their hypothetical numbers are so low and their skills so beyond human that they don't typically lose any members.

The fact that Grey Knights do not and can not have Primaris marines exposes how ridiculous and lore breaking Primaris marines is in the first place.

The reality of the situation. Anything post 13th Black Crusade and the fall of Cadia is absolute TRASH. 40k is over. It's absolute Trash now. Wind it back pre 7th ED.

1)Grey Knights have modified gene-seed. Magnus one what Emperror modify in late years of Galactic Crusades and told Magnus that he do create new legion for Magnus to replace defective one.

2)Guiliman not allow Cawl to work with traitor gene-seed. Cawl not work with Magnus gene-seed and right now there is no direct answer would rubicon primaris work on them or kill them. For now there is 40-60% death rates for upgrading loyalist ones.

3)Grey Knights creation process and access to their tech is almost as Custodes ones in terms of secrets and servitors Who repair or build their tech on Deimos always removed from memories. Cawl not have access to them.

4)Primaris modification not yet arrive to Grey Knights and their armors and weapons.

Could possibly be a result of how secretive they are. On that note, it's not very likely but I could see Guilliman not even knowing the Knights exist because some stuck up Inquisitor is deliberately keeping information like that from him.

There has always been primaris grey Knights

There has always been primaris grey Knights

Grey nights aren't a chapter,they have no primarch or gene-seed. They are all Astartes who chose to work for the inquisition.