Well, I've finally got my finger out after figuring out I had a dodgy cable (don't buy cheap camera cables!) and have given the theory a try....
It's almost worked, apart from the lag on the Mumford or my flash is quite a bit more than I'd hoped for. There appears to be about 1/10th delay between the sensor triggering and the flash, way too long, so I'm not even getting the felt in shot. I also managed to shoot myself in the groin with a cleaning felt whilst I was setting up, missed the important bits but it did make me jump.
Here's a picture of the space left after a pellet has passed through, you can still see small fragments of paper in the air. The reason for the sheet of paper was to establish if I was too late rather than too soon (paper intact = too soon, paper with hole or on other side of room = too late). Being indoors there's no muzzle blast but I bet you'd see some outside in this weather.
I'll give it another go with a CO2 pistol but I think it's the lag rather than pellet speed. On some of the shots the paper had moved a couple of feet but was not blurred so I need to have another look at the manual or try a different sensor perhaps to try and get something more immediate. It was actually triggering from the slight click coming onto the 2nd stage before you release so the clip on vibration sensor is sensitive enough but need to look at how I can reduce the lag.
For this one I had the flash set on manual at the lowest possible power setting to give the shortest flash duration. The lens is 24mm and the camera was on full manual at F22, ISO 200, and the exposure time was 1.3 seconds.
ISP Airstream MK III No 15 which is a bit poorly at the moment and having a rest
AA Pro Sport + Ginb FT8 stock + Bushnell 4200 6-24x
EV2 MK1 + Leupold Comp 40x
Weihrauch HW100 KT laminate
SBFTC Competition Secretary