A scope is the only way to make these shots... and it had better be a damn good one! Duplex crosshairs are a must but I prefer windage hash marks on my deer rifles/shotgun scopes. Boone and Crocket Mil-Dot and Varmint Reticles give you an instant measuring device for lead time/distance.
Consider....
How far should you lead a whitetail buck running broadside at 30 mph @ 100 yards.
Time of bullet flight will be just near 100 m/secs or, 1/10th of a sec. || .10 times 44 fps = 4.4 foot lead for a chest hit.
How far should you lead a whitetail buck running broadside at only 15 mph @200 yds?
Average bullet flight time is going to be around one fifth of second or .20 of a sec., [15 mph times 1.467 = rounded off 22 fps] 22 times .20 of a sec= 4.4 foot lead ahead of the heart and lung area on that trophy whitetail buck, that is about to go out of sight and escape if you don't drop him in his tracks.
Here is a site that should help you... read
http://www.udarrell.com/leadingrunninggamerifle.html