I am the owner of Steinert Sensing Systems, maker of the SuperChrono. I am posting this in response to the comments about links to our website not working.
That's correct, the website has been hacked. It's been unavailable since August 17th. We have moved to new, ultra-secure server to make sure this will not happen again. The website will be available again shortly.
As for reviews there's one in the October issue of Guns: The Speed Read | Guns Magazine
The leading German magazine Visier tested the SuperChrono against a pair of reference chronos and found deviations of just .15% or just a few feet per second. You'll find this on our web site when it becomes available again.
The main thing about the SuperChrono is that it has to be aimed carefully and aligned with the bullet path. If you use the spirit level instead of the sights the readings will be off by about 200 ft/s.
The spirit level is there just to give you a general idea during setup with the tripod. If you place the chrono directly on the ground without a tripod the shockwave will reflect upwards and the readings will be off.
Place the SuperChrono 10 feet in front of the muzzle for most loads. Magnum loads may have a longer muzzle blast and to make sure you get reliable readings, place it 15 feet in front of the muzzle.