The standard finish for US military wooden stocks has been boiled linseed oil. There is a version sold under the name Lin-Speed Oil, which is linseed oil and a solvent to speed up the drying.
Follow directions with the product you buy, and do NOT leave laying about the rags or paper towels you used to wipe down the surplus. Linseed oil reacts with atmospheric oxygen, generates heat, and will set rags on fire when you REALLY did not expect that!
What we have here is... failure- to communicate.