“It is only the usual trouble about words being used in more than one sense. Thus we might say a man ‘became a soldier’ the moment that he joined the army. But his instructors might say six months later ‘I think we have made a soldier of him’. Both usages are quite definable, only one wants to know which is being used in a given sentence.”
— C. S. Lewis to Genia Goelz (March 18, 1952), Collected Letters, 3:172. Quoted by Justin Taylor in C S Lewis on Theology and Worship
In other words, Scripture teaches that baptism converts the sinner (see e.g. here, here and here) while at the same time saying that conversion is a pre-requisite for baptism (see e.g. here, here and here). Nevertheless, I think Scripture's emphasis is clearly on the former given that it speaks unambiguously and in the majority of baptism making people Christians.