Board Thread:General Nerf discussion/@comment-27306930-20190505214335/@comment-27306930-20190506003135

The Chrono Barrel appears to have one infared beam. Depending on the mode, the ammo counter is either increased or decreased each time the beam is broken.

Measuring FPS is slightly more complicated. In order to calculate speed with one beam, you need to know the length of the dart. The chrono simply measures the amount of time the beam is broken and does some basic math. A Nerf dart is 2.75 inches, which is .23 feet.

So if the beam was broken for .0033 seconds then (.23 feet) ÷ (.0033 seconds) = 70 FPS.

Unfortunately, the ChronoBarrel will only work with full length darts. But for 8 bucks it's still a pretty good deal.