Range finder is only a 10% buff to range. Not really needed on a scout rifle. Firefly is always good. A reload perk like outlaw/feeding frenzy is good or rodeo/counterbalance to reduce the recoil. Explosive rounds can cause the firefly explosion not to activate so I don't like weapons with both perks. Armour piercing rounds are good, especially for the first part of CE. As you can get several head shots with each shot, causing several explosions.