Thank you guys for your feedback, all of what you guys said is honestly true.
The models of this pack were all made in Milkshape 3d and I haven't learned Blender by that point yet, not to mention I never really was a "pro modeller" in the first place. I'd possibly ask someone like Khain to help me out with the models and, to be honest, I always considered my models placeholders.
Regarding particles and other stuff the muzzle effects are just shamelessly stolen from Bushido's Adventure Pack and could really use some work as well.
As for theming, I actually was just pulling random guns I liked into the pack and compiling them not by theming, but by weapon type - "I need an UZI, a rifle, a shotgun, etc..." so I didn't even consider things like making them all modern-themed or WW1/WW2-themed. My goal at the time was to get all the systems going with functional guns that felt fun to shoot and reload.
I want to ask, though, do you guys feel if the actual gun balance is good? I wanted to make sure that every gun stood up on its own and could counter any other weapon in the pack in the right hands.