This here is some impressive strobist work. A quick peek at the exposure info explains a lot. 1 second exposure @ F/13, ISO400. That means the photographer had some wiggle room to trigger the gun and the strobe, yet didn't have to worry about ambient light making the pellet appear blurred. What I surmise he did was trigger the gun and strobe simultaneously, and had a digital delay actually fire the strobe X milliseconds later. Knowing the FPS of the pellet and how far it had to travel to pass the razor, it would be reasonably easy to compute. Getting a shot like this actually work is a whole nother matter. My hat's off to him.