In order to make your own weapon, you're going to have to script & model.
As Darius said, you can learn scripting yourself, and modelling isn't too hard either.
Here's a great tutorial for Milkshape 3D, hopefully it can get you started:
http://halflife2.filefront.com/file/Milkshape_3D_SPAS_12_Shotgun_Modelling_Tutorial;36160Here's a tut on how to model & package/export everything so you can use it in Blockland:
http://forum.blockland.us/index.php?topic=18088.0