For manual reloading system go to entities > Gredwich's stuff and spawn an ammo box, then press E on the ammo box and find 81mm, Click on it and then press HE or Smoke shells (Smoke spawns smoke and HE is just normal missles) Some mortals require 82mm shells (Same HE or Smoke).

A little bit same with guns, for example there's a gun named 155mm M777, the word 155mm says itself, It requires 155mm shells. It also requires HE or Smoke shells depends on what gun is that.

so thanks