Which sniper rifle has the least knockback?

So I’m trying to shoot the guard that sits down to the left of the spa (Om Edwin) in Haven Island by luring him round the wooden wall by shooting the wooden post, where he dies he’s in the bushes, safe, but this annoying waiter prick goes back and forth the place where he can be found and if you interrupt his cycle once he redoes it, so there’s a 10 seconds wait from Jason Portman’s hut as a sniper spot before I can finally shoot him but then the Sieger 300 backboosts him all the way out of the bushes so that he can be found by the guard that patrols behind that area (even if i shoot him in the torso with the Sieger 300 Ghost). I have plenty of time to bring out one of the non-Sieger snipers that take years to bring out, please inform me on which sniper is the best to pick in this case.

ICA Woodsman is money.