I've tested mine with a handful of shells using the "other" and "handgun" settings (changes where it asks you to position the muzzle relative to the chronograph). It read 12 gauge shots consistently but the numbers seemed a tad high, I think that the Doppler effect + muzzle velocity back calculation method that it uses may not work accurately when faced with multiple radar returns like you'd get from the shot column and wad flying out there.