You can cast Float to Time inside the Metasound. So changing ShotInterval to float and casting it where it is used, fixed the problem. Also remember to create new GameplayCue tag for new weapons and make your GA_Weapon_Fire (or child blueprint) to use that as “Gameplay Cue Tag Firing”.
The metasound parameter “Shot Interval” is connected to Fire Delay Time Seconds inside GA_Weapon_Fire. For every weapon, you can create a reference for its correspondent fire rate and get it inside any child of GA_Weapon_Fire. Please check that section again.
Open the object and navigate to the section “Process target data once ready”. Then, get the node "Make Gameplay Cue Parameters from Hit Result, left click in its return value, drag and release. A window will pop up, then select “break gameplay cue parameters”. Select the set variable GCNParameter, left click on the left blue pin, drag and release, and select "make Gameplay cue parameters. Take the newly created break and make nodes, connect everything but Normalized Magnitude. In this one, connect Fire Delay Time Secs.