Hi,
First, I suggest you to open MAX and check your webcam settings. You should set the "Video Mode" to the good resolution and framerate.
Then in the status bar you should check the actual acquisition and display framerate. Save your settings and go back to LabVIEW.
Also never forget that if you use image processing, you may decrease the framerate due to the use of your CPU (for instance, your saving function to BMP may take time depending on your HDD speed and decrease your framerate)
Regards