Bob, weave, duck, and wear a full face helmet.
But on a more serious note. The three things that I know of (and I am no gunsmith mind you) that control where an empty casing goes are 1) the ejector, 2) the extractor, and 3) the recoil spring. Maybe a different length ejector, a different tension on the extractor, a different weight recoil spring, or some combination of these three.