See, I told you some folks don't like PACT! I do trust mine though, but I may have just gotten a rare good one.
When I first got it, I put it back to back with an expensive Oehler 35P
(really great chronograph but expensive and was discontinued for a while during which Oehler focused on other products. Looks like they may be available again now but for even more $$ than before). The 35P actually has 3 sky screens, they call it a "proof channel", so it takes two readings itself - one from sky screen 1 - 2, and one from 2 - 3. These two readings seldom agree exactly, but are generally within a few fps of each other. When the same bullet passed over the Oehler and the PACT, my PACT was consistently within 5 -10 fps, usually slower, when in front of the Oehler, and within 10 - 15 fps, again slower, when behind the Oehler shooting my USPSA .40 load. With my PACT, I could actually "compensate" for this difference by doing some calculations and setting the sky screen distance to some fractional number over the factory set 24" (Since mine is a hair slow, I would need to tell it that the distance is a hair over 24". If the bullet is covering a longer distance in the same time, it would read faster). I haven't bothered though since the difference is so slight and I know where it is, speed wise.
Since that time, I have shot essentially the same USPSA load and been chronographed in major matches in Mississippi, Louisiana, Alabama, Georgia, Tennessee, Illinois, Missouri, Ohio, Texas, Oklahoma, and Nevada, largely on CED chronographs but not always, and in weather ranging from summer in the desert to just above freezing. I haven't had any surprises. My standard procedure is to load my match ammo and go test them on my PACT here in Mississippi. At the matches I have always been within a reasonable variance of my results here. Generally the match chronos show a bit more velocity.
'Neck, I have one question. I guess I don't understand the recommendation to "get a Chrony" followed by "you get what you pay for" and going cheap and regretting it. The cheapest PACT is about the same prices as the most expensive Chrony, isn't it? And the top of the line PACT is about twice as much as the most expensive Chrony. I generally tend to believe that you get what you pay for in many, if not most, instances. So I guess my advice is to get the Oehler I mentioned above! Ha. Seriously, sounds like lots of folks are happy with the Shooting Chrony's.