yes, the mosins are drying up. In the states, they are all selling over $300 now. When the current ones run out here, expect a price hike.
As for the finish "rifle stock oil", the real stuff has no pine tar in it at all.
Over on GB, someone found the original mix in a finnish manual and it was translated as follows:
Ingredients: BLO, naphta, bitumen (roofing asphalt is usually made of bitumen) and red iron oxyde for punamulta
Start by diluting the bitumen in naphta until it has the consistency of milk. Add BLO to it making sure that the overal color of the mix remain pitch black. If you mix in a glass vessel, the liquid should look black but the deposits on the side of the glass should appear dark brown. Mix a tiny amount of red oxyde with blo and mix super carefully. You don't want a paste. Add naphta until the red is like milk as well. Add little by little to the other mix, testing the color on scrap wood each time.
The guys experimented and came up with:
2g of red oxyde
8g volumes of bitumen
110g of BLO
30g of thinner or Turpentine for thinning the bitumen
for a result of 150g of Rifle Stock Oil
Personally, I would recommend turpentine over napthalene. Naptha has benzen in it, a known carcinogen.