I refinished a muzzle loader stock that was built from a kit back in the 1970's. The stock was sycamore that seems to get harder, pores get smaller with age. Oil based stains like Minwax wouldn't penetrate, even after prepping the stock with alcohol. I was told, water based stains would work better.
I ended up making my own stain by filling a glass jar half full of white vinegar, adding some steel wool and old nails and letting it sit a couple months.
Turned the stock a beautiful brown while enhancing the grain.