The away side elected to field, but Lincolnians began well by posting 201-8 after their 40 overs in this Lincolnshire County League Fourth Division match.
Steven Pratt led the way with an unbeaten 58 while wickets were taken by Ben Wilkinson (three), Matthew Pearson (three), Stephen West and Tom Wilkinson.
With the bat, Horncastle were dismissed for 60 with no batsman able to reach double figures.
The Sunday Firsts were beaten by eight wickets at Scothern in the Lincoln and District League Division Two.
Nathan Whiting (37) and Reece Brant (20) helped them to a total of 100.
But Scothern replied with 104-2 in the 14th over.
Gareth Jones and Reece Brant both took wickets.