I'm not an expert, but I did some research on many chronos some interesting stuff. Two come to mind.
One is the Velociradar, and Caldwell customer service told me on the phone that pellets might be problematic,...soooo, that's out.
Two is the LX, which uses a combination of sound trigger, then radar takes over. If there is no sound, then the radar won't do a thing. Now, I know you can get microphones etc but not ideal for pellet rifles. The website still hawks the LX, but 2 out of 3 sites I checked shot discontinued. So, my guess is it didn't compare well to the Garmin and Athlon, so why waste money making something that won't sell.
Funny side note: I saw a youtube video of a guy shooting rubber bands off his fingers and the LX recorded every one, and he wasn't using any kind of mic. ???