In the case of handgun rounds, larger caliber bullets tend to be flatter to prevent over-penetration leading to collateral damage. Smaller-caliber bullets tend to be rounder (so called “round nose” ammunition) so they penetrate more, giving a greater chance of having the desired effect on the intended target.
There’s a LOT more to it than that, but that’s the quick and dirty answer. There’s also hollow point ammunition, which is a whole other rabbit hole, and we haven’t even talked about rifle cartridges yet, which can have wildly different bullets for all kinds of applications.
The reason why Glocks have that characteristically square slide is so the sights can be as low and as close to the barrel as possible. There’s a very long-winded reason as to why this is a good thing on a handgun. See the “bore-to-sight distance” section here for that: https://en.wikipedia.org/wiki/Bore_axis
First, some terminology. A “cartridge” is fully assembled and ready to fire. The “bullet” is the projectile that comes out of the barrel.
Some cartridges do have bullets with a flat nose, like the .40 s&w fmj cartridge pictured here. https://en.wikipedia.org/wiki/.40_S%26W
Some bullets are even “flatter”, like wadcutter rounds, which are designed to cut clean holes in paper. https://en.wikipedia.org/wiki/Wadcutter
In the case of handgun rounds, larger caliber bullets tend to be flatter to prevent over-penetration leading to collateral damage. Smaller-caliber bullets tend to be rounder (so called “round nose” ammunition) so they penetrate more, giving a greater chance of having the desired effect on the intended target.
There’s a LOT more to it than that, but that’s the quick and dirty answer. There’s also hollow point ammunition, which is a whole other rabbit hole, and we haven’t even talked about rifle cartridges yet, which can have wildly different bullets for all kinds of applications.
The reason why Glocks have that characteristically square slide is so the sights can be as low and as close to the barrel as possible. There’s a very long-winded reason as to why this is a good thing on a handgun. See the “bore-to-sight distance” section here for that: https://en.wikipedia.org/wiki/Bore_axis