"The .22 Phillips Screwdriver Mod"--TAOFLEDERMAUS (12 min.)
The gist of the video is that the producers took standard lead hollow point .22 LR and, pressing a #0 Phillips Screwdriver tip into each cavity, scored and began the mechanical process of opening up the hollow point. They then tested it against various targets, including a "Gummy Bear" target made of ballistic gelatin. In my link, I have started a bit over 9 minutes into the video to get to the important part, which is where they dig the bullets out of the gelatin. The producers of the video say that bullets expanded to roughly two times the normal diameter, so that seems to show that the modification worked as intended.
I would also note, however, that the bullets were not able to penetrate through the target. I don't know the thickness of the "Gummy Bear" target, but it doesn't look to be more than 6 or 8 inches. This suggests that these would not be good for defense against a human target. But for hunting small game like rabbits or squirrels this appears that it would might be worth the effort.