Why don't bullets used in guns have sharp corner edges? Why don't bullets used in guns have sharp corner edges? Like why are they spherical or smooth at the tip? Is it to avoid air resistance?
But as my sir told that how speed we move proportional we get sir drag as it is Stokes law.
 A: It's a trade off with small returns at the margins of accuracy vs other factors. This is really an engineering question.
Pointy bullets lose less energy to drag thanks to a lower drag coefficient, meaning they have superior performance at extreme range. Rifle and artillery projectiles usually have this shape.
Rounded bullets fit the desired amount of metal into a shorter projectile and are less prone to getting stuck on things, meaning  they are slightly more convenient and reliable out of a simpler machine. Pistol projectiles usually have this shape, since handguns aren't accurate at ranges great enough for drag to matter.
There are also small tradeoffs in tip design, armor penetration, expansion, fragmentation, and so on.
Ultimately the differences are minimal unless you're shooting hundreds to thousands of meters away.
A: I'm pretty sure that the shape (and orientation) of a high speed object does effect the frictional drag. The cylindrical shape of a bullet relates to the fact that many guns have “rifling” in the barrel to give the bullet a spin and stabilize its orientation.
A: High velocity rifle bullets generally do have pointed tips, whereas lower velocity bullets are often more rounded. Not all bullets with supersonic muzzle velocities are pointed but it is preferable for anything with a supersonic velocity to have a pointed shape to minimize drag from the shock waves. This includes leading edges of supersonic aircraft wings and tail surfaces as well as their nosecones.
A: To add slightly to this discussion, bullets used for short-range target practice with pistols can be bought with completely blunt front ends. When these "plug-cutter" bullets strike the paper target, they excise a round hole the same diameter as the bullet- which is easier to see at a distance.
Aerodynamic drag is not an important consideration when shooting targets with pistols at a range of ~ten meters, so the plug-cutter design does not compromise accuracy during pistol-shooting contests.
A: 
why are (all bullets) spherical or smooth at the tip?

They aren’t. Some bullets (generally called spitzer bullets) do have pointed tips.
