I have messed around with timer sensitivity. At my range with the two types of timers, I have I would get all kinds of echo with my open gun. I don't think adjusting the timer sensitivity between shooters is the way to handle missing shots on the timer. I also believe the use of a phone to time is a bad idea. They are expensive and I find them less user-friendly than a timer. You know I think its a gun issue. You want to go at it from another angle have you tried contacting the companies that make the timers we use now? They might have an answer for you?