Arduino | pulseIn times out before expected?

Hello all!
I'm trying to read values from an ultrasonic sensor with an Arduino. For some reason, when using the pulseIn function, the value of pulseIn starts to return 0 far before expected. When I give it a timeout value of 888, I can't get it to return values of >240. Any suggestions?

withinInches is a float value set to 6.0
speedSound is float value set to 0.0135 (inches/usec)
Using these two values yields 888 as the rangeTimeout

Thanks for your consideration!

Edit: Full code can be found in the following link, but since the ultrasonic sensor is only one component of my project there is a lot of code irrelevant to this post.
Full Code