The wedge controls the end gap between the cylinder and the barrel. It should be about .006". The further the wedge is driven in, the less gap there is. As Fedaircop has found out if you drive it in too far the cylinder will not turn freely in response to the hand and the revolver will be difficult to cock; in an extreme case the cylinder will not turn at all.
The wedge screw function is the subject of some debate. There is apparently evidence on Colt's patent drawings that it is intended to indicate or perhaps control how far the wedge is driven in; I've been unable to make that work on any of my Colt replica revolvers. However, it does have another function that I'm sure of: it prevents the wedge from being driven completely out of the barrel assembly; the screw head catches on a lip on the end of the wedge and it hangs loosely in the slot when that lip contacts the screw head.
Fedaircop - don't worry about spelling or grammar errors here. Everybody makes them, some are so bad as to make the post illegible, but there are no spelling mafioso here. Or if there are, they don't last long. We tend to forgive as long as we can figure out what we think you meant.