Could FPS of a pellet be actually measured in 1920?

[evert]

Hi, I remember about 50 odd years ago!] my uncle Stan built a machine, it was a rotating electric motor driven shaft which he attached 2 cardboard discs at one foot apart. He had worked out the RPM some how? & by some mathamaticle equation ? he could work out the FPS when a pellet was shot through the 2 rotating discs. I have never seen one since, regards Al.

I dream of building something like that, its simplicity is just very appealing.
But there are too many other projects on the list...