I've put Brownells Teflon/Moly on my 870 pump and Mini-14 and it's great.  Now I'm thinking about using GunKote on my Walther PPKS.  Thing is I really don't want to take all the springs out of the gun.  Would heating up the springs to 300 degrees hurt them.  I'm kind of worried about taking the temper out of them.

I don't believe 300 deg would affect them.  I do think it would be nessissary to take it apart anyway and coat only the parts you want on the surfaces you want.  I think it would look much cleaner and the chance of the coat getting into the action or the oil coming out onto the finish wouldn't be worth the risk.  At 300 deg the oil becomes very thin and the smallest ammount will leak out.  I saw a shotgun barrel that was powder coated and the seam by the breach had oil that leaked and ruined the powder coat so it had to done all over again.

 Bake away.