I can see 30 caliber bullet holes in regular paper targets with a good 8x Leupold scope, unless lighting conditions are poor.
A good 3 to 9x variable would be a fine choice (stress good - magnification does NOT translate to visual acuity - I can see more detail with my good 14x than with a cheapo 30x spotting scope). Much more magnification that that and it gets harder to find your sight picture. My son's 3-9x Leupold will almost see 7 mm holes at 200 yards - meaning that under the most ideal lighting conditions, you do see them. With the "shoot-n-see" targets you can get away with less magnification or less quality optics.
Why bother to even bring up the ability to see your bullet holes? Because knowing where each shot lands gives you valuable feedback on each shot so you have a better idea how you're doing. That’s important-- it's how you develop the ability to "call your shots".
You can shoot excellent groups with no scope at all, for instance, but you won't know it until you either sight through a separate spotting scope or make the walk. Then you may discover you have a flier or two, but you have no idea which of your five shots were the flyers, so you're missing important information about your performance.
20x is big overkill unless you're trying to read the dates on coins at 100 yards. I would guess that you'd not be happy with 20x as it limits your field of view such that finding the target becomes more difficult, and your eye position behind the scope has to be super precise or you see nothing. A friend of mine recently installed a 20x scope on his long-range 7 mm mag. My son and I both did better than he, me with the 4-14x (at 14) and my son with the 3-9x (at 9). He (Mr. 20x) spent most of his time trying to locate the 4" targets at 380 to 500 yards. Some people do very well with high magnification scopes, but they have a lot of experience with them. Regardless, they are slower in target acquisition. I find them irritating to use.
A good shooter with good equipment will be able to shoot groups approaching 1 MOA with iron sights at 100 yards, whereas the same shooter, assuming the rifle can do it, might be able to shoot a half inch using a scope. The rare shooter/rifle can do better yet. The best five-shot groups I've gotten with my Rem 700 are just under 1 MOA, at 100 and 200 yards.
