My preference is not finer than 20 lpi. for a hunting rifle. If I lived and hunted in an area where a fellow wasn't wearing mits or gloves for half the season then 22-24 might be O.K. . Don't know. It takes good solid wood to hold finer than 20 lpi. when used in the field not to mention the difficulty of checkering a piece of soft wood with finer lines than should be used. 20 looks pretty good if done cleanly. Even 18 is good for a knock about hunting rifle and gives you an excellent grip even with gloves on.
