Snap-shooting over the top of the bunker is one of the trickiest snapshots of all. You are more exposed and it is much slower than snap-shooting from the side. However it is a crucial move and one of the most common mistakes is getting too close to the bunker.
If you are able to position yourself slightly back you can allow your barrel to just barely touch the bunker as you snap over top and then be completely out of the way on your way down. This will keep your shot more accurate and you'll be able to come down quicker and prevent your gun and loader from staying exposed too long.
Make sure you check out my other snap-shooting videos and use the invisible line method to help create a sight picture before you even snap out.