The right-arm medium-fast bowler, who moved to the County from Lancashire during the close-season, recorded six for 34 in a superb showing.
Rory Kleinveldt grabbed two for 72, including his 400th first-class wicket, as Durham were dismissed for a meagre 166.
But Northants ran into trouble in reply, losing three wickets before the close.
They ended the first day of the Specsavers County Championship Division Two clash on 59 for three, with Max Holden (19no) and Chesney Hughes (16no) the men in the middle.
And Buck said: “It’s about time I took a six-for, but if I can do that it shows it must be doing a bit.
“The ball bounced a bit and there was good carry. It swung quite a bit at times, but didn’t nip that much off the pitch.
“The way Max Holden stuck in at the end shows what can be done and it’s a big day for us tomorrow.
“The way we lost our last two wickets was unlucky, but Chesney was looking good.”