Gangta made a strokeful unbeaten 111 off 158 balls with the help of 12 boundaries and five hits over the fence to help Himachal Pradesh post 300 for five in their first innings at stumps on the second day in reply to Jammu and Kashmir's 293.
Besides Gangta, Robin Bist also chipped in with a handy contribution of 66 that came off 137 balls and was studdes with seven fours, while wicket-keeper Ankur Bains made 37 up the order.
For Jammu and Kashmir, pacer Ram Dayal (2/63) and skipper Parvez Rasool (2/76) picked up two wickets apiece.
Earlier, Jammu and Kashmir could add just 19 runs to their overnight score before being bowled out for 293.
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Skipper Parvez Rasool remained stranded on unbeaten 114 as Himachal Pradesh polished off Jammu and Kashmir's innings in 4.5 overs of the morning session.
Rasool's century knock came off 185 balls during which he hit 10 boundaries and three sixes.
With figures of four for 107, Rishi Dhawan was the most successful bowler for Himachal Pradesh.
Jammu and Kashmir 1st innings: 293 all out in 94.5 overs (Parvez Rasool 114 not out, Rishi Dhawan 4/107).
Himachal Pradesh 1st innings: 300 for five in 83 overs (Nikhil Gangta 111 not out, Robin Bist 66; Ram Dayal 2/63).