By interpreting your question as "Can most hotends print polycarbonate at 300°C+?", and taking into consideration the answers to Can cheap hotend parts sourced from China actually produce good prints?1, then it would seem to be safe to assume2 that most hotends can, given a few adjustments or considerations:
- Use of a PT1003 or thermocouple, en lieu of a thermistor
- Use of PTFE tubing
Taken directly from E3D's V6 product info:
The V6 can comfortably reach 285°C with the supplied thermistor. By swapping a thermistor for a thermocouple (may require additional electronics) or PT100 you can reach over 400°C. This not only allows you to print extremely high temperature materials like Polycarbonate and Nylons but also eliminates HotEnd meltdown failures associated with PEEK/PTFE designs. The PTFE filament guide inside the V6 HotEnd is never subjected to high temperatures, so there is no risk of damage through overheating.
1 The materials used by cheaper clones of the higher quality, more expensive, branded hotends are probably the same as those used in the branded hotends, and indeed are probably produced using the same pirated patterns/molds/casts, but with less care and quality involved. They can even be produced in the same factory, but are items that have failed the QA tests, and as such are not deemed to be brandable.
2 Although, to paraphrase a quote from a movie: Assumptions can be considered to be the mother of all disasters.
3 A Pt100 or Pt1000 is a Platinum RTD (Resistance Temperature Detector) with a resistance of 100 ohms at 0°C which changes with temperature. From this manufacturer's website:
A Pt100 or Pt1000 is a Platinum RTD (Resistance Temperature Detector) with a resistance of 100 ohms at 0°C which changes with temperature. They are suitable for applications in the temperature range of -200°C to 600°C but are more commonly used in the range -50°C to +250°C. These temperature sensors are reliable and can offer a higher degree of accuracy.