Gonna post this here to help others out.
This is a small bit about serverpackages
1) Open UCL file for the weapon you are adding with notepad.
2) Go to the third line (weapon=)
3) It should look like this:
Weapon=(ClassName=BDHuntingRifleB2.HUNTING_RIFLE,PickupClassName=BDHuntingRifleB2.Hunting_RiflePickup,AttachmentClassName=BDHuntingRifleB2.Hunting_RifleAttachment,FriendlyName=BDHuntingRifleB2.HUNTING_RIFLE.ItemName,Description=BDHuntingRifleB2.HUNTING_RIFLE.Description,FallbackName="Hunting Rifle",FallbackDesc="A recreational hunting weapon, featuring a firing trigger and a powerful integrated scope. ")
4) Take out the bolded part. Remember, your pickups should always look like MUTATOR_NAME.SOMETHINGRELEVENTPickup. If you have a comma in there, you're doing it wrong.
5) Put that in your custom trader file.
6) Go to Killingfloor.ini and open it with notepad
7) Scroll down to ServerPackages= and add your own line of that
8) Add the package file. Basically, for weapons you just want to take out the part BEFORE the period in your custom trader entry, like so:
BDHuntingRifleB2.Hunting_RiflePickup
Note: You will see the bolded text SEVERAL times in the .ucl so that's how you can tell what to add and if it's the right thing to add.
Not sure if the mutator.u can have a different name then the filename so, just to be safe.