The wording for this achievement may be quite confusing.
By 'Sniper mode', the game is referring to a 'skill shot'. If you are unsure what a skill shot is, you can check the Rules section from the menu.
However, here is a more detailed description:
When you plunge the ball at the start of new ball, you will see one of the table's ramps light up (full red). If you can successfully hit the ball up the designated ramp before the lights extinguish (it only stays lit for a few seconds), you are awarded a 'skill shot'.
Each time you start a new ball, you have an opportunity for a skill shot.
Skill shots earned while playing the 'Bloody Challenges' also count, as I earned the achievement during one of the challenges.
Be sure to use a table you are comfortable with if you are having issues.