Sprite mask and sorting group issue

Hello,
I'm having an issue with the sprite mask and the sorting group.
I have a character having a sorting group with an external sprite mask :

So the character can be seen behind the obstacle, I want to do the same with the weapons that the character can wear :

Weapon hierarchy (He has a Sprite mask that doesn't work)

And that's where the problem lies, I want to sort my character with the weapon, I need to instantiate in the sorting group :

The full hierarchy in game

If I don't mask for the weapon :

The weapons of the character are spawned, so I can't make an external mask and he has multiple type of
weapon so the size can depend.
I am open to the solution and would like to discuss it.

Unity version : 2021.3.8f1

Thank you in advance