The visitors got off to a strong start after opting to bat to finish the day at a commanding 310 for three.
Chopra
ended the day unbeaten on 168 that came off 299 balls. He hit as many as 24 boundaries.
Chopra and Ankush Bains, who made 47, raised 120 for the opening wicket.
After Jaydev Unadkat cleaned up Bains, Chopra and Ankit Kalsi (37), added 81 runs.
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But Chopra shared an unbroken 73-run alliance with Robin Bist (30 not out) to take Himachal Pradesh's total past the 300-run mark.
Saurashtra bowlers had a tough time as four of them conceded more than four runs an over.
Brief Scores:
Himachal Pradesh: 310 for three in 90 overs (Prashant Chopra 168 not out; Jaydev Unadkat 1/45).