The answer about recoil starting when the bullet moves is correct. We noticed when shooting pistols that hot loads shoot lower than light loads (that seems to be the opposite of what you would think). The explanation however is that hot loads allow the bullet to exit the barrel before the barrel has time to rise as much where as with a lighter load the barrel rises more before the bullet get out the end. That is a similar result with a rifle and part of what you were attempting to get at. I believe that final sighting should be done as close to hunting conditions as possible. If you shoot off hand final sight that way. If off a rest use a similar rest at the range for sighting and so on. I try to set up my hunting stands so that I rest the forearm on a log or tree limb at about the same loacation on the forearm that I use at the range on my rests.