Usually they are some sort of pistol scope if they are that far upfront. I had one on a pellet gun I had years ago because I wanted it mounted on the barrel vrs the reciever of the rifle. They make regular scopes which are around 3 inches or so, then shotgun scopes that are over 4 inches and then you get into the pistol type scopes. They work ok at lower powers, you get to 4 power or above and the are a bit hard to line up without having the lens black out on you. The alignment to your eye becomes more critical as the power and distance increases.

Another thing to consider with scopes is the parallax. While they may focus on the same plain they are not accurate at all ranges. Most rifle scopes are set for around 100 yards. At closer distances the parallax will be off. If you are not perfectly lined up with the scope every time the bullet will not strike the same spot. This increases with magnification as well. This is why Adjustable Objectives or parallax correction is so popular with target shooters or high powered scopes. They are more precise, but take longer to focus for the shot.

You can check for this by putting your scope in a rest and aiming at targets at different distances and moving your head around while looking thru the scope (do not move the rifle). If your scope is not parallax free at that distance the cross hairs will move in relationship to the target. This is the amount your shot could be off.

So a quick shot up close with a scope set for 100 yards may not be any more accurate then open sights will be. Depending on how good your shooting form is and how your scope is mounted. Another reason why see thru mounts can cause problems. It makes it difficult to have a proper cheek weld to the stock in order to have repeatable form from shot to shot. Of course they will be plenty accurate to kill deer at moderate distances. I just wouldn't enter a shooting contest with high rise scope mounts and a non parallax adjustable scope is all. Open sights sit very low on the rifle and are much quicker to line up on when you snap the rifle up quickly.

Paul