A sight is a firearm accessory that assists the gunner in aiming and observing the bullet point. Its form can be divided from basic to advanced into the simplest "light gate+collimator" mechanical sight, holographic and red dot represented speed sight, and the most advanced magnification optical/electronic sight.

The sniper gun uses a high magnification sight, which can magnify the target by 3 to 10 times and kill targets hundreds of meters away. As is well known, the sight glass and barrel are not in a straight line, but in two parallel positions - the sight glass is either installed on the side of the gun body or on top of the gun body. But this design does not affect the sniper's performance.

Didn't the bullet come out of the barrel? The aiming point of a bullet is higher than the starting point, why can a sight that is not in a straight line with the barrel be able to hit where it points?

To explain this issue. Firstly, we need to talk about what trajectory is. The flight trajectory of a bullet is not a straight line extending from the barrel. After the warhead is loaded, air resistance will cause its flight heading to deviate slightly to the right or left, while gravity will gradually cause it to fall, forming a parabolic curve.

If you aim directly from the back of the gun with the barrel, then due to the influence of gravity, the farther the distance is, the lower the aiming point the bullet will appear. It's impossible to hit a distant target at all.

So, the line of sight of the sight is not parallel to the barrel. Taking a mechanical sight as an example, its line of sight is the three points and one line of sight of "light gate+sight star+target". Although the aiming door is above the barrel, the height from the aiming door to the barrel axis is greater than the height from the collimator to the barrel axis. The "two points and one line" from the collimator to the aiming door is called the aiming baseline, which means that the aiming baseline is a diagonal line intersecting the barrel axis.