The usual reason why a servo has a top limit of 270 degrees is that the position sensing pot which is directly connected to the output gear has a track that covers 270 degrees. That is how they have been made since the first days of electronics. The actual servo travel might well be mechanically limited to rather less than that by having a lump on the output gear, and matching lumps inside the case. This stops the pot from going where it shouldn't and destroying its wiper.
If more travel than a morph can give is needed, use gearing, or gearing and a morph. Or a 2 turn winch and program the transmitter to limit the travel to 300 degrees down from it's natural 720. The winches are usually a normal servo with the end stops missed out and an extra internal gearbox between the output gear and the pot.
The only way to tell if the ebay ones can do that is to get one and look inside. If it has a direct connection to the pot, no. Otherwise, maybe.
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Topic: 180 and 270 degree servos (Read 1801 times)