This is a model of a type of musket ball. There are many varieties, and they're commonly referred to as Minié balls after the inventor of one type. I'm not sure which kind this actually is. The dimensions are accurate for one particular variety of rifle ball, but the rounded point is borrowed from other types. In any case it's a basically accurate representation of the class of musket balls even if it's not an accurate representation of a specific variety.
Obviously this is not meant to be fired. Trying to shoot it would probably not work well, but it can serve as a model for conveying the shape and size of the real thing. I really just made it because I was surprised not to find one already on Thingiverse. The dimensions of the original were given in inches, so I used those to model it and scaled it to mm. I've provided a version in inches, though, and the
.scad file has a scale factor so you can change the units if you want.