Different thermistors have different maximum tolerances, and I know that the one MakerGear uses is different from the one E3D uses, but the temperature issue may be about the temperature at which you damage the thermistor, not the temperature at which you damage various parts of the hot end.Set the HotEnd temperature to 285ºC. If you did not do a PID tune, then approach this temperature slowly, exceeding 295ºC will permanently damage the thermistor.
On the other hand, that statement is at odds with the following comment I got from someone at E3D in an email:
They must have swapped out their thermistor for another to get the temperature up to 420 (420?!). I will have to ask them what measures they took to get the temperature up that far without melting everything.Every one of these filaments in one form or another has been printed by us: http://e3d-online.com/Filament (And many others, up to 420C)