All of our chronographs use  our MVII Skyscreen System (and optional IR system) and detection circuitry, so far as bullet detection goes they are equally accurate. If you are just looking for a solid little chronograph to give you velocity data the PACT Model 1 is for you. If you are an Action Shooter, by all means get the PACT MKIV Championship Timer and Chronograph.  All our Chronographs are made by us here in Texas and are backed by our 30 Day Money Back Guarantee.