Change Ammo Model On Firing

[MrAcid]

Just as the title says...

 

I am working on some custom weapons for a mod, and I've created a special ammo for one weapon. The problem is that it looks really stupid when it loads. The custom ammo model being sort of a glowing particle orb.

I am using the Rocket Launcher as the basis for the weapon. I wanted to know if there was a way to have it show the regular shell when loading, and only show the special ammo model when it fires.

 

Thanks for any help.