My rule of thumb for current factory guns costing under $1000:
Percentage of lowest local price for a new gun.
Test fired only- (as new with box papers etc)- 85%
Excellent- No pitting or buggered screws. Spotless bore, no "handling" marks or dings, etc. 75%
Very good- No pitting or buggered screws. Light rub and or "handling" marks (no dings) indicating light or careful use, excellent bore. 65-70%
Good- Light pitting around breech or muzzle, minor blue or finish wear, small dings and light scratches on stock, bright bore, no buggered screws. 50-55%.
Unless the price is very low or the gun is very special, I avoid guns with buggered screws, because if bubba can't figure the right screwdriver to use- he probably didn't know what he was doing once he got inside.
Thus a rifle in very good condition, that's available locally for $399 l would look to pay no more than $275
Just my $0.02