For what it is worth, there are some interesting photos at www.african-hunter.com/recoil_vs_accuracy.htm. (You can get there through their archives if I botched the address.)

Stock build, the width of the stock and recoil pad and of course rifle weight have a whole lot to do with recoil for me. My son's 308 Tikka kicks more than the 338 Win Mag I had. I believe there is recoil as soon as the bullet leaves the casing, and the barrel reacts as the bullet goes down the bore. But the rock & roll really starts, as far as I know, once the bullet leaves the barrel and gasses escape freely. Otherwise, we would not hit much. But I am open to other thoughts. What the heck. It is an important topic.