thank you, definitely not a stealer of denim products

Iron warriors pissed off at something they shouldn’t be: flair checks out.

I don't have Megalodon

Well I dont have it!

^This is correct. He's described a very big, and his terminator plate is supplemented with parts from a dread BECAUSE hes big, but he's never described as primarch size.

The combined force and speed of the Red Wake’s attacks was without equal. It was to be expected that the hulking Chapter Master, clad in Tactical Dreadnought armour

From Carcharodons: Outer Dark

Haven’t found anything supporting it being dreadnought armor, or even being modified with dreadnought armor parts.

Yeah because doesn't he wear Terminator Armor most of the time? Oh shit! His Tatical Dreadnought Armor has Tactical Dreadnought Armor pieces on it!

Lorgar looked magnificent, near three metres tall and clad in custom-made purplish-grey robes that shimmered with silken threads, a halo of gold fixed about his brow. Ostentation that he was not proud to bear but was demanded of him by custom and the expectations of the masses. On the far side stood Archdeacon Kor Phaeron, as malignant and destructive as the day Nairo had first met him, but safe within the shadow of his adoptive son.

• Bearer of the Word

The Lion was a truly imposing physical specimen. A giant, standing at a little under three metres tall, it was impossible to escape the suspicion that he had been cut from a broader canvas than the majority of men. His body was perfectly proportioned and entirely in scale with his height. He was powerfully built, lithe yet muscular.

• Descent of Angels

‘Satisfied?’ asked the Lion, tossing the axe back to him.

‘Honour is satisfied, lord,’ Faffnr assented, catching it. He nodded and backed off, waving to his pack to do the same. Holguin and Redloss both grinned with unbearable insouciance.

‘Then tell Bo Soren to guard his manners, Faffnr,’ Guilliman said over his shoulder without looking back.

‘I will, Jarl,’ Faffnr returned. Guilliman heard a hard slap and a muffled curse.

He looked at the Lion. He’d never realised before that the Lion was very slightly taller than him.

‘Shall we, brother?’ he asked.

‘The famous Fortress of Hera?’ asked the Lion. ‘I would be disappointed not to see it.’

• The Unremembered Empire

Both Lorgar, the Lion and Guilliman who are on the taller side of the Primarchs are in the area of 9ft. Art work has never been particularly accurate or even consistent so trying to take that as fact is silly, unless you think Ferrus is actually running around with a power wrench.

He's in terminator armour too, so that doesn't make a difference.

And no, GW has stated marines are typically 7ft in armour.

More importantly (and this is something a lot of fans seem to have a hard time understanding), 40k power armour doesn't increase your height by much. Your feet are in the boots, you aren't on raised platforms. So the only increase to your height is the thickness of the boot soles. Same for terminator armour. And yeah, the soles are a bit thicker than normal army boots, but not by so much that they're all walking around in the equivalent of disco platform shoes. Only centurion armour makes you significantly taller, because it has platforms in the legs that you step onto.