In a closely-contested match at Castle Park last Friday evening, Duns came out on top and also secured the bonus point for tries.
Langholm finished with a losing bonus point and were a bit unfortunate not to get a draw following late pressure.
Understrength Langholm went in front with a try from centre Jack Fraser, but the home side replied with a score from fly half Hayden Martin which Dale Robertson converted.
Dingers winger Scott Maceachen got their second try and after the referee allowed a glaring knock-on by the home side at the restart to continue, Ben Black got their third.
Langholm replied with a penalty by Martin Chisholm and try from Calum Bell which Rudi Marshall converted to make it 17-15 at half-time.
A Nathan Smith try converted by Chisholm put Langholm in front at 17-22, but Martin had a brace of tries for Duns, one of which Robertson converted.