As a sniper you can get the Snap Shot skill in the Marskmanship tree:
- Level 1: Entering cover has a 50% chance of making the next Snipe activate instantly. This effect cannot occur more than once every 6 seconds.
- Level 2: Entering cover has a 50% chance of making the next Snipe activate instantly. This effect cannot occur more than once every 6 seconds.
As the skill describes getting into any cover will grant you a 50/50 or a definate instant snipe depending on your level in it, however from personal experience this is false.
When entering your deployable cover and having the skill at level 2 there is indeed a 100% chance of instant snipe, but using hard cover (rocks, terrain, etc.) there is still only a 50% chance at level 2.
Workaround: Don't have anything targeted when you enter cover, that will make you enter cover where you stand (deployable cover) rather than roll to the nearest pebble.