The Quality Armory has a bug: when you attempt to shoot a nearby player, the weapon won't fire and you'll perform a simple melee attack.
This data pack checks each tick is a player hold a crossbow (the QA's gun are crossbow with a skin). If so, it sets the entity interaction range to zero, disabling any melee attacks and forcing the weapon to fire.
Note that this won't work if you're in Creative mode, for some unknown reason.
IMPORTANT : Because the "Entity interaction range" was officially implemented in 1.21, the datapack wont work in older version
If you need help (or have advise) with the datapack, you can join my discord server :
https://discord.gg/DHQgwH9GuG
If you need help with the QA's plugin, join the support server :
https://discord.gg/p2hnWBB6M4
Here's a link toward the Quality Armory page :
https://www.spigotmc.org/resources/quality-armory.47561/