Here's how I get the wedge out on mine. Using the bullet of a cartridge (or any suitable tool), push down and in on the spring end (the grooved end). Push the wedge in or through as far as the tool allows. If the tool is a cartridge, use the bullet end to push it in, then use the rim of the cartridge to lever it out from the other end. At that point, the wedge should be far enough out to pull it with the fingers.
If the spring tab is sharp or has burrs on it, it can be smoothed up; it should be flat or a bit rounded on top.