In a frantic finale, Rundle scored his second try of the afternoon to condemn his old side to defeat and clinch a nail-biting 29-27 away win in National Two North on Saturday.
The Black Country outfit were fast out the blocks and hooker Jack Lea scored in the first five minutes.
But Tynedale weren’t behind for long as Guy Pike crossed – the conversion was unsuccessful, but Rob Parker’s penalty soon had the hosts in front.
Rundle then claimed his first try inside the opening 20 minutes before two quick-fire converted scores established a 22-12 half-time advantage for the home side.
Stourbridge attacked the restart as quickly as they had begun the game and Joe Heatley powered over shortly after the break with Chris Scott adding the extras.
Lea then applied the finish to good forward play to edge the visitors into a 24-22 lead, before Pike ran in his second score of the game for the home team. It looked to have sealed the points for Tynedale, but Rundle crossed from out wide to have the final say and snatch the win.