Yep, I reckon from about 350 degrees to maybe 380 degrees is about an optimum temperature setting range for most solder-joints in a guitar, the higher side of the range is good for when you go to solder a ground-wire to a pot since the metal casing soaks up the heat like a sponge soaks up water, the typical 60/40 solder has a melting-point of about 250 degrees (it could be a bit more though), when the solder cools it goes from a molten-state to a solid state, but, there is a very narrow-margin where there's a "Plastic" state, you normally find this Plastic-state in plumber's solder, but in 60/40 Solder this Plastic-state is deliberately made to occur in a very narrow margin within the temperature range as the Solder cools-down and goes from a liquid to a solid-state.