I set two up in tandem, an RCBS unit and Chrony F1, and fired several strings of different calibres through them both, comparing the readings.
There were not any wild fluctuations shot to shot, and the readings were consistently close with the F1 generally reading about 15fps faster. Loads were 270 Win, 7mm RM and 308 Win.
I bought a chrony F1 about 15 years ago. It was and still is my first chronograph.
On an overcast day it seems to work pretty well and consistent. Sunny days and especially sunny days with snow on the ground it seems to have readings that are less consistent, and some missed shots.
I always set it up 30 feet in front of the muzzle.
Overall it has served my basic needs for working up loads rifle and handgun loads, and fiddling with rimfire velocity checks.
If I ever upgrade I'll go with one of these strap-on bayonet style Magnetospeed chronos that do not rely on light at all, and don't need a tripod or any 'lining up'.
I've used an Alpha Master Chrony with at least 15-20 rifles and have shot many of those out to 800+ yards with good results. Dead nuts with JBM. Actually killed the original body with a bullet, and the replacement worked just as well as the original.
I've also shot the Chrony in series with a Pro Chrono and they were within 2% or less as I recall. They both stopped "reading" under the same low light conditions. I do a lot more load work during the fall, winter, and spring so most of the time its overcast. Direct sunlight on the sensors is an issue, but I just stack boxes and whatever else is handy to provide shade... no problem.
I shoot in the coast mountains, but if I were using a chrono at a formal range I'd rather have a remote to reset the chrono, turn it on or off, etc.
In rain, my buddy has a plexi-glass cover for the Pro Chrono but the rain drops screw with the readings. I've thought about using a cardboard box with a hole in the top covered with a white kitchen bag. Have never needed to do it though.
I have zero complaints with the Chrony but like Shane, if I were to upgrade or start over I'd look at the Magnetospeed.
