I am finishing a rifle now using curly maple that has a similar situation. I am not sure what caused it, but the section in question has a smaller amount of curl verses the rest of the wood and is more dense than the rest of the stock. This grain ran down one side of the butt and came back in the bottom of the forearm. There are no cracks or anything. The only issue I had was that it did not take stain as easily as the rest of the stock. It is the first time I have run into this since I started building in 1978. The butt section came out really well, but the forearm is still a bit lighter than the rest of the stock. It is going to turn out to be a nice rifle. Just gives "Old Covid" a bit of character. Odd thing is that I have not owned a rifle for the past 12 years, and am building this rifle using parts I have had put back for several years for myself. Go figure!!
Roger Sells