If you haven't gotten to the staining part of building your gun don't worry.
You say "with a lot of curl..." and if the curl is showing up nicely on a unstained piece of wood it will REALLY show up after staining.
Folks who are new to working with Curly wood often don't understand exactly what they are looking at.
The newly sanded wood will have sort of an iridescent striped look but it really isn't very impressive.
The curly woods aren't really curly. The grain is wavy. It looks like this little drawing.
The waves get cut off when the wood is machined or sanded leaving the "end grain" showing between the normal grain that is parallel to the surface.
Those end grains will absorb a whole lot more stain than the parallel grained areas so they will end up MUCH darker. That is when you can really see the stripes.
As was mentioned, the high priced high quality wood will have many more stripes and they will be fairly uniform thruout the length of the stock.
The lesser (and more affordable) woods may end up with some "open" areas where there are few stripes but for the most part, if you bought a good piece of wood the open areas will just add some interest to the overall look of the gun.
If you can't wait until you get to the staining part of building, use some fine sandpaper to sand the bottom of the barrel channel smooth. Then apply a little ALCOHOL BASED stain and let it soak in and dry. Maybe a couple coats of Walnut?
Then take the stock outside into the sun and dampen the stained area with a wet rag. THAT is what it will look like after the finishing oils are applied.
Oh, without applying the finishing oils the look of the stained area will return to a rather unimpressive "colored wood" look when the water drys.