Except that it is not? The line in the middle of the bullet is where the case would start. The case would be bigger than the bullet and have a groove at the end to insert and eject the case in the gun/ magazine.

https://en.m.wikipedia.org/wiki/5.56%C3%9745mm_NATO#/media/File%3AGP90.jpg

That was my biggest thought about the intro sequence to Lord of War, too.

That’s 70% more bullet. Hard to argue with the math.