Depending on the date of your 03-A3 RLO or raw
linseed oil
or Tung oil could have been applied when it was made, the U.S. started using Tung oil in 1943.
There is only one place I know of that sells real pure Tung oil and that is at this link......
Environmentally Friendly Paint - Real Milk Paint ® everything else on the market presently in nothing more than a wiping varnish no matter what the label tells you (read the msds sheet on each product)
A conservator in a museum to clean an antique firearm stock would use a 50/50 mix of raw
linseed oil
and turpentine, a soft cotton cloth and a heat lamp to help sweat any impurities to the surface. The metal parts of the gun would be cleaned with pure raw olive oil and a soft cloth and possibly a soft bristled tooth brush to lightly scrub some areas.
At the far end of the Bubba extreme spectrum some people would put the stock in the dish washer.
What lies in the middle is to determine what type of paint is on your stock and how badly you want to remove it. At repair level shops and at overhaul your stock if needed would be scraped or sanded as needed to return it to serviceable condition.
NOTE: Your rifle would not pass military inspection at any level with paint on it and something would have been done to it to remove the paint. Scraping seals the pores and surface of the wood and sanding opens the pores of the wood (What type surface do you need to match?)