Darkening light wood has always been a holy grail for stock finishers, and about as difficult to obtain with any degree of success, i.e. having light and dark spots and/or dull and shiny spots in the finish.

What you are looking for is an alcohol=based penetrating stain. Last time I looked, Brownells had some. I've used the Pilkington stains sold through Brownells with good results, but there's a learning curve as in most gun finihing/refinishing.
JR

Be strong, be of good courage.
God bless America, long live the Republic.