Multiplier Stacking in CW (How well does Deathknell stack with Kurnous' Precision?)

As far as I know, there’s a multiplier on Crits & Headshots, which generally is the same, and then there’s a multiplier for critical headshots - and these may differ depending on weapons.
I do also remember that this modifier is usually capped at 1. WHC supposedly has a hidden 25% hs damage multiplier bonus, and deathknell adds another 50%. The same would be true for Kurnous’ Precision, which can be randomly rolled in the chaos wastes.
Now, a heavy charged attack from the Rapier already hits the damage cap on a critical headshot, but what are everyone’s experiences with more realistic use cases? Will a non-critical charged headshot still benefit from the extra talent (against regular armour), or does it hit the hidden multiplier cap?
I am aware that this might be rather hard to test.

edit: While we’re at it, is there a source of such numbers as the base multipliers on specific weapons? Last I’ve seen that showed all the data was years old.

Edit: Turns out I did put this where I just started it because I wasn’t sure where to put it. Sorry about that.
If any moderator sees this, I would be quite content with this being moved wherever it supposedly fits. I felt a somewhat technical question definitely concerning one specific game, but being neither a bug, nor really feedback, kind of didn’t quite belong anywhere. I think it should go into feedback, though.

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