Hunter's hand Gun, craftable, can be loaded, won't fire. Everything is being done right, but it won't fire. RIght click does nothing. Controls are all correct.

This is likely mod interaction issue as that code hasn't been touched in ages.
Have you got it in a modpack?
Can you try with just Reliquary if so?

it is not in a modpack, its seperate
is there other mods that i need for it?

No other mods are needed.
I have just tested with just reliquary and it works for me. you're right clicking to fire, right?

Im using it in an Aternos server, 1,10,2, I will show you a list of the mods, dont know if any of them would conflict
https://cdn.discordapp.com/attachments/494331707017658368/538415544446091279/unknown.png

On single player it fires extremely slow. I have used it in a modpack before (Infinity lite) and it fired just fine, beautiful. Do you think any of those mods conflict it in the image list i sent?