Nah. You wouldn't want any of those rifles.
They all have straight octagon barrels on them.
(Except for the second from the top)
The only darkening agent used on any of these was a wash of lye water which brings out the tannin in the wood.
I see folks talking about the hard and soft areas of curly wood.
That is kinda right but it doesn't tell the whole story of why these woods have stripes.
Curly wood like curly maple doesn't have straight grain like normal wood does.
The grain is wavy like the lines in this sketch:
Where the waves meet the surface, they are cut off leaving essentially the end grain showing.
End grain will release more tannin with the lye water treatment than the grain in the areas where it is running parallel to the surface.
It also absorbs more of the stain/aquafortis than the parallel fibers so it ends up darker.