You can get at about 95% of the internal parts in a 99 just by having the buttstock off and if he replaced the wood already I'm pretty sure he's oiled and cleaned as much as he can already. I'd hazard a guess it's the hammer spring, can't see it being anything else if it's hitting the primer.

I'd also make **** sure it hasn't been in a fire like you think cause if it was there is a chance that the heat weakened the steel and then your looking at losing a hand if the gun does fire. Just my .2, hate to see anything happen to a fellow Savage nut.