I have found that on the Crony (I have the cheapest one) if you don't shoot right down the middle you will get high readings for some reason. Also you should use the sky screens unless it is a uniformly cloudy day. Otherwise it is a useful tool.

Several things come to mind and I don't find your experience strange, its about par for the course...

One thing is barrels can vary 100 FPS or more in some cases with identical loadings, not unusual at all, we have fast barrels and slow barrels...

Another thing is some folks load hotter than others, I have found some of the most experienced shooters load hotter than the neophite, also not unusual..Many folks load overly conservative and of course they are not going to extract the best the gun has to offer..also few actually work up the max load for their individual gun and rely on reloading manuals, which should be only a guide for beginning your workup...I, load many calibers a grain or two over book max and a few below book max....

Quality of the chronograph is another factor, you simply get what you pay for like anything else..

some chambers are tight and some are loose and that seems to change things to one degree or another..

Many shooters shoot a round through the chronograph and accept that as fact, nothing is further from the truth, you will get a rude awakening if you shoot 5 or 10 rounds, toss out the high and low shot and take an average..

As the barrel gets hotter you will also see a rise in muzzle velocity..

Lots of factors cause the problems that some are makeing light off, but in fact, they are not someones imagination, they are caused by a combination of the above and other events that take place on the testing range, therefore we must remove the varibles and take an average of I suggest 10 shots well spaced, thats the best we have, and its a hell of a lot of trouble, is it worth it, I doubt it in the case of a hunter or from a practical point of view....It does matter froma safty point of view.

I shoot a minimum of 10 rounds for record. I would like to shoot 20 but sometimes I want groups also. I then use my cheap TI calculator to calculate X bar (average) and SD. I calculate SD because it is easy, but I am not sure of it's usefulness. Since some loads with high SD's seem to shoot fine.

I wore out two Chronys, a Beta and a Gamma model, both with printers. I found them to be persnickity, particularly on bright sunny days or bright days with floating clouds. Alignment was extremely important at all times. Before I got the printers I had trouble reading the speeds on occasion, the screen looked like 888888 many times. I always used the sky screens and they wore out first, but still considered my info fairly accurate for 4 years. I then got my Oehler 35P and found out what reliability and accuracy really were all about. I also learned that some of those bright sunny day readings on the Chrony were extremely fast. Good shooting.

That is VERY funny.

This is good to read. I just got a 35p after using a chrony for some time. I never trusted the reading and just quit taking it. I now intend to test everything again.
I believe that most of the difference between manual information and what reality gives us has to do with the rifle/barrel combination. The older manuals listed specifics about what was used including the fact that the test rifles sometimes used barrels 3 to 6 inches longer than the sporters we were testing. Loads and charge weights have changed dramatically over the years and everyone needs to stay aware of pressure signs and changes in the norm when we start experimenting.
Even joking about trying to reach higher pressure may cause problems with the uninitiated or foolish who may decide to "try it out" and end up with a piece of shrapnel (sp) between the eyes.
Just observations.
Frank