Or you can borrow or buy a cronograph with a big measurement surface (like the Caldwell Ballistic Precision Chronograph) that I use for arrows, and put it close to the target. U can have the speed at any distance.
I've just got a few days ago Westhunter FFP 6-24X50 (https://www.aliexpress.com/item/32922692642.html?spm=a2g0s.9042311.0.0.345e4c4dt78LR0). It's writen 15 yards on parallax wheel but i can get a clear image in 7-8 meters on x6 magnification.