YOu can have "realism" by imparting script damage [which amounts to \target.health = target.health - [whatever]\] based on several factors, but at the end of the day, it's never going to be an intuitive experience.

So, I've been making weapons mods for my personal use. I know how to set the weight of the round, but does anyone know how to to explosive rounds?

Depends on what you can do:

The old way was shooting MOSParticles [MOSRotating?] that gibbed whenever they hit something.

The new way involves attaching a lua script to a MOPixel, or whatever you are using, and making it detect when it is going to hit something, via casting strength rays, and making it spawn an explosion when it detects something hittable, or an actor.
Azzuki's Experimental Sniper Rifle has a script for such a bullet, and in the Minor Mods Thread, I think it was called the IWS, it was some kind of animated mortar that shot proximity charges in a similar fashion, the IWS is somewhere in the more recent pages of the thread.

try increasing the particle count of the bullet.