so first after picking up ur own gun, u need to set up a trigger + attach a timer to it, then start editing the parameters, go to "gun" trigger actions, and select the related trigger on the displayed image:
then simply there is a step that may help more, prob u can edit the projectile model to have different look so use this trigger on the related image, u may be able to change the model by inserting a number from the projectile models list
https://plazmaburst.miraheze.org/wiki/List_of_projectile_models:
then something should look like this:
but please make sure to convert the projectile first then change the model by index or else issues will appear, properly my thoughts that the projectile aint appearing because there might a reason behind using different types of guns, and yes that is why there was something is missing, because u can only use the invisible gun, but if u want to use other guns like the assault rifle and then converting then it might be more likable to not using so many triggers when u want to mod the gun.
please re-follow the steps to make sure what u have made from mistakes...
if u want further info about the index models whatever..u can check that blog:
https://www.plazmaburst2.com/level_editor_manual/projectile%20model%20indices.html