Hello Asish. You have secured a good rank. Your chances of getting a government college for Mtechi in Mechanical is good but you'll have to wait for later counselling as the 1st round seats usually close at around 400. But there are chances that you may not get the best colleges.

Hey. 

U may get a government college if you belong to one or St/Sc . Because the first counseling include rank between 1-300 ,  2nd 301-450 . U may get a chance in 3rd counseling if seats would be left. 

Hope it helps. Best wishes