Hello,

Yes, you can score more than 300 in JEE  main paper 2 considering that you have prepared well and have a strong command on the subjects. Now, if you score more than 300 marks then your rank will be under 800 and you can easily take admission in NITs with this rank. Generally a general category candidate need to secure rank under 1500-2000 to become eligible for admission in NITs and they need to score around 250 in JEE main paper2.

You can check the link below to know about the previous year cut off rank in NITs.

https://engineering.careers360.com/articles/jee-main-cutoff-for-b-arch-b-planning

Good luck!