It is a fake weapon, so, the geometry is does not matter. Anyway, it should not work as real.
So, you can left it, with no geometry at all:
GeometryName = ""
Or give geometry of your scondary real weapon like this:
GeometryName = "all_weap_inf_sniperrifle"
Real weapons, by my method, should always be secondary. Reason: you can switch them only once, and it stuck, with fake weapon.

Understood you, I'll try!