I used a Competition Electronics ProChrono for almost 30 years
until it died from being abandoned in a closet for a couple of years.
It worked flawlessly if you did your part.
I now have the replacement:
ProChrono Digital
and a Magnetospeed V.2 which also works well.
The Magnetospeed does have a drawback in that it is barrel mounted
and as such can't be used on revolvers shorter than about 6".
Pistols with moving barrels/housings are also out.
Works fine with a pistol like the Ruger MKII though.
No affiliation, just a happy customer etc....
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Nemo