While this can be done, it is not recommended for the following reasons:

• The Gate Timing measurement for the speed of the projectile has greater error than you get using Pulse Timing.
• You must manually set up Logger Pro to treat the Projectile Launcher as if it were a photogate. Any change that triggers Logger Pro to auto ID the connected sensor will reset the program.

Here are instructions for setting up Logger Pro to measure the speed of the projectile using the ball’s diameter instead of the distance between the two photogates.

1. Connect the Projectile Launcher to your interface. Connect your interface to your computer.
2. Launch Logger Pro.
3. Choose Set Up Sensors from the Experiment menu, and select Show all Interfaces.
4. Click the square next to the image of the interface that corresponds to the port in which the Projectile Launcher is connected. The square should show the picture of the Projectile Launcher.
5. Click Choose Sensor > Photogate to have Logger Pro treat the Projectile launcher as a photogate.
6. Click the square (that now shows a picture of a photogate) again and change the current calibration to Gate Timing.
7. Click the square a third time, select the Set Distance or Length option and change the length of the object to 0.017247 m, then tap OK.
8. Close the dialog showing the picture of the interface.
9. Choose Data Collection from the Experiment menu and change the mode to Digital Events.
10. Adjust the End Collection option to end as follows:
    If you are not using the Time of Flight Pad, choose to end collection after 2 events.
    If you are using the Time of Flight Pad, choose to end collection after 5 events*.
11. Click Done to exit the data collection dialog.
12. Delete the Velocity and Gate Time graphs. (Click on a graph to select it, then press Delete from your keyboard.) 
13. Choose Meter from the Insert menu and select Digital Meter. This should bring up a Velocity meter.
14. Choose Auto Arrange from the Page menu to adjust the table and meter to fill the Logger Pro screen.
15. Load the projectile into the launcher and pressurize the chamber.
16. Start data collection in Logger Pro, then fire the projectile. 
17. Repeat steps 15 and 16 as desired.

* Note: If you are using the Time of Flight Pad, you will get two Velocity measurements, one for each photogate in the launcher. Use the first measurement.