Ed,

In the EMER’s I have for the L42/L39’s it mentioned the following this I would be the “Hains” manual for this particular rifle:-

16A. To obtain a uniform colour, woodwork is to be treated with a stain mix from the following ingredients: -

4 oz Dye, solution, dark brown oil (H1 (b) / 6020-99-224-0037)
2 gal linseed oilicon, raw (H1 (a)/ 8010-99-942-7803)

Mix the dye with the linseed oilicon and heat to 100 0C, stirring while heating and then allow to cool. Remove old wood surface with coarse abrasive and finish with fine abrasive. Immerse the woodwork in the solution for one hour, remove and drain off over the tank and wipe off surplus. The stain may be applied to handgaurds and other small components with a pad of soft cloth

17. Linseed oil is to be worked well into the wood. If the woodwork appears dry the items may be soaked in linseed oil, for half an hour. After soaking allow draining off over the tank in cool dry air.