It looks like the old-time gangsters had a flair for the tacticool, even way back when. I guess it never really goes out of style. People have been making their weapons "better" and more "tactical" since the first caveman started sharpening a stick.
It would be amusing to see what Baby Face Nelson, Clyde Barrow, and other infamous desperadoes would carry if they were given access to the modern selection of high speed mall ninja accessories.
Well, maybe not amusing if you were getting robbed, but this is an idle thought experiment.
I'm guessing it would be all flash. Probably some kind of M4 supershort auto with fancy grips, lights, lasers, and all kinds of other holographic tactical accessories. I bet those guys would have loved that sort of thing.