I would be tempted to do a very light stain more of a wash coat to increase the contrast, but the grain is so nice on those already maybe oil alone will make them pop, then what ever is your finish of choice. Might be worth testing on the scrap wood. Oil, diluted spirit stain and finish only. I would also look at some muzzle loaders for comparison. Some of these were treated with Aquavit, Iron Oxide and vinegar, Potassium permanganate and flame finishes.

I hope you saved some of the straighter grain wood for axe handles or other tool handles. The lower two I can picture the stock already, the upper one doesn't have as obvious a layout on it.

"When you disarm the people, you commence to offend them and show that you distrust them either through cowardice or lack of confidence, and both of these opinions generate hatred." Niccolo Machiavelli