Dead by Daylight

Down and Bound

The first introduction to a reticule or Aim Down Sight on a Killer or Survivor!

As you may have guessed from the previous line. We have the Deathslinger! A rooty-tooty-point-n-shooty gunslinger named Caleb Quinn. His power being The Redeemer. An engineered gun to shoot a spear and Reel in his prey; like fishing but with humans. Apparently ordinary bullets were too mainstream.

The Method:
Windows, Vault Points and Funnelled Areas are your bread and butter for this achievement. I wouldn't waste your time with Pallets. You get the hit but no progress or a down against the Survivor and rightly so, considering the distance.
Once you're in a chase. Get the first hit with your basic attack to put them to an Injured State then just keep up with them. Stay close enough to know where they're running but not too close to get 360'd. Wait for them to Vault, Climb, Fall or funnel themselves. With any Vault, you'll have to lock and shoot as quick as you can. Distance + Angle + Obstacles = Time. Should be the formula you'll subconsciously use with every shot. It's trial and error along. With your 10 second hold without Add-Ons. Should help time your shots.
Use Caleb's Tall silhouette! Most loops you'll end up running. You should be able to shoot over the top when you're approaching the corners.

I found this very effective and got the achievement in about 5 games. Although some of you will be naturals shooting with the Deathslinger and others will want this achievement to just come with time. Caleb is a fun Killer to play as so there isn't a rush to get this out of the way, play the way that makes you enjoy the game.

Range:
I'd always take the shot at mid to close range (as a Killer without Add-Ons).
The shots are very temperamental. Some that clearly hit, don't hit and the ones that really didn't. Hit.
It averages out, a little like the Huntress with her Hatchets.
Close range. I'd advise against since it's easier to dodge. Regardless, as long as you get the shot and down the Survivor. You'll get your progress.

Remember: 100% of shots not taken are 100% shots missed.

I hope this helps!