The best replacement for firearm is weapon.

The best alternatives to firearm are rated as following:
★★★★★  weapon
★★★  gun
★★★  deadly weapon
★★  taser
★★  firearm
★  fire arm
★  dangerous weapon
★  rifle

Your alternative for firearm is not listed? Suggest!
Speaking about firearm, one probably shouldn't forget about felony.

Other search terms related to firearm and their ratings are:
★★★★★ felony
You have in mind a companion for firearm and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of firearm in all years. Click on graph for more.
firearm
weapon
gun