Sherrell,
When working on kits pre-inlet for a barrel (which typically don't have any scrap sent with them) some builders will lightly sand a few spots in the bottom of the barrel channel and use those as a test areas. You just have to be careful not to overdo it, and don't sand the sides that fit against the barrel. And if you used an acid-based stain, then neutralize it well.
Most antiques were not stained in the barrel channels, or in any of the mortises, for that matter. Obviously, it's not necessary. Moreover, nitric acid-based stain (which was commonly used on Maple) has potential to rust steel, and so there are advantages to not putting acid stains in a hole into which you plan to put a piece of steel.