Absolutely concur with Brian and Cinder's. I can't abide varnish on a military rifle.
I think many cases of what appears to be varnish are a historic build up of boiled linseed oil... It achieved the same result over time.
The process of removing all this accumulated crap, the use of scotchbrite and raw linseed oil, will bring the wood roaring back to life, nourishing and allowing the wood to breath again. The results can be dramatic and very satisfying.
One word of caution, just noticed your stock appears to be the "ersatz" laminated type.
I haven't personally restored one of these before, anything to watch out for with these when restoring guys?