If Protection from Normal Missiles or Shield was available in the Spell List, would it protect from Starfinder Lasers or Machine Guns? I know there's Resistant Armor spells and I guess Blasters and Phasers and such are an "energy type" but what about 20th Century and later guns? Surely a bullet is a "normal missile"? So if I allowed Protection from Normal Missiles would it work vs Modern Firearms?
Every ranged weapon that hits KAC shoots normal missiles of some kind.
Considering the 3rd level Starfinder spell for defending against bullets provides DR 5, allowing a 3rd level Pathfinder spell that grants DR 10 seems radically unbalancing (let alone the 3rd level D&D spell that confers absolute immunity).
If the old spell worked well against Sci-Fi bullets, they'd still be using it...
Do you mean Protection from Arrows?
If so, it would have no effect against lasers, plasma guns, flame guns, or any other energy weapon since DR has no effect against energy-typed damage, in either Starfinder or Pathfinder. I would assume it would otherwise work against projectile weapons in the same way the spell works against firearms in Pathfinder - as long as the weapon isn't Hybrid, it's DR 10 (since I'm guessing the hybrid part would overcome the DR/magic).
As far as Shield, it would now provide an Enhancement bonus to AC (likely both, given the original spell was also designed to gain a bonus against magic - much of which targets EAC now if it targets anything at all).