When I set up for a shot like this the gun is obviously benched. the load is chosen to get as close to 1000 fps as possible to help "find" the bullet in the air - .001 sec = 1 foot. The plane of the bullet's path must be located carefully to locate an infra red beam for it to break. There are a number of tricks that can help here - it just takes time and trial and error.
With patched ball shots I extended a ramrod out of the barrel and positioned the IR beam to be broken by the rod end. The camera was aimed at the rod.
Swiss Powder would be used instead of Goex because Swiss charcoal is more finely ground, eliminating sparks which interfere with the shot.
When all is correctly aligned, the camera settings checked, the shooter aims the rifle and signals he is ready. The lights are turned off the camera shutter opened for a brief period (3-4 seconds). The shooter fires, camera shutter closes, and lights turned back on. We look at the photo and make corrections and try again.
If the patch is still on the bullet, we move the shooting bench back and try again. By adjusting the bench, we continue until we see the patch separate.
If I were to try this with a 540 gr bullet I would want to see the bullet stopped in outside tests before moving inside. My neighbors still think I'm a nice guy.
Regards,
Pletch