This mod brings most of the weapons from GTA V to IV. This mod is still WIP. The weapons which were added in the DLC (updates) have been modeled from scrach while others are converted from GTA V. Following are the weapons which are converted
AP Pistol , Golf Stick , Combat MG , Stun Gun , Bullpup Shotgun , Assault Rifle , Gusenberg Sweeper , Pistol , Marksman Rifle , Musket and Antique Cavalry Dagger.
How to install
1.) Start OpenIV or SparkIV
2.) Open weapons.img (located in pc\models\cdimages)
3.) Import the weapons from the .rar file
GtaForums link = http://gtaforums.com/topic/699100-wipreliv-gta-v-to-iv-weapons/
Don't redistribute , modify and redistribute the model without permission. You could modify it for your personal use.