Do you want to add and use firearms even in survival mode with a mod from your world to destroy all the mobs in the game including your friends? then use the Mod Guns mod.

The mod will not only work in survival mode, which means you can start real wars with your friends in a cubic universe. Shotguns, rifles, pistols, grenades, grenade launchers, armored jackets and much more with this mod

DISCLAIMER: This is an unofficial application for Minecraft Pocket Edition.
This application is not affiliated in any way with Mojang AB. The Minecraft Name, the Minecraft Brand and the Minecraft Assets are all property of Mojang AB or their respectful owner.
All rights reserved. In accordance with
http://account.mojang.com/documents/brand_guidelines