Hello Srijith, 

The NEET cut off varies from year to year, state to state and as well as college to college. It also depends on the Quota you are applying through as well as the Category of Admission. Government and Private Colleges have cut-offs of their own. 

Assuming you are applying through the 15% All India Quota under General Category for a Government Medical College, the cut-off for NEET 2017 was Rank 5579 which corresponds to a score of approximately 520 marks out of 720.

This year, there is expected increase in the cut offs. With a score of 310 marks, your expected rank should be between the range of 1,70,000 to 1,72,000.

Your chances to get a medical seat are very bleak, let alone Karnataka. All the very best!