Make particle scale up as it moves away from the camera?

I’m using particles for simulating bullets flying through the air, and when they get some distance away it gets really hard to see them at all. So I thought a way to fix this would be to scale the bullet particle relative to the distance it is from the camera.
I managed to get the distance from the camera in the material (particle position - camera position), but I’m not sure what I can do with that in the material editor.

(absolute world position - particle position) * “distance from camera” into the vertex shader

you’ll probably want to get the distance from camera into a range that gives you the desired visual result but all in all this should be what you want. might have to switch the order of operands for the subtract, not sure right now.