Even if the gun was not built to fit him, if he brings his eye lower (backward on the stock) either it will shoot even lower or he wont be able to see over the breech. Exception would be if he was crawling the uppermost nose on a pied de vache stock.
I am probably just worn out and cant think today.
ok think on this
Lets say your eye is level with the rear sight on a rifle . IE you can look strait through the sight . Everything is 0 . You bring the front blade up and all is good right ?
Now lets say you are looking down at a positive angle . Basically your line of sight is just a little high . Now whats going to happen is your eye isn’t going to give you a true reference. When you bring the front sight up . What looks like level is actually a little low because of your line of sight .
So if your face is alittle farther back . Thus little lower .. Your line of sight is not strait down the barrel . Thus the front blade must come higher in order for you to get a sight picture .
Or think of it this way .
Your shooting an O to R barrel with ohm? A 16 in octagon section . Your current line of sight lets you see the full 16 inches . So you bring the blade up and use the top barrel flat as a reference . But your shooting say 10 inches low .
As you move you face slightly back , you see less of the length of the flat even though you can clearly still see the flat . because you see less of it , you have to raise the muzzle more , in order to see the front blade