In Factorio, you have 3 slots in the bottom corner of the screen which can hold 3 different weapons. Alongside them are also ammunition slots, with each of them needing to be filled with the appropriate ammo type for the guns to function.
With your weapons, there are two different firing modes available. An automatic lock, which only works on nearby enemies (hold SPACEBAR) or a targeted shot, where you can shoot anything your cursor is hovering over (press C).
Below, you can see some tips for using weapons and switching between guns. For more Factorio guides, make sure to check out our dedicated area here!
Switching Between Guns in Factorio
When you first start Factorio, you will only have a Pistol available. By unlocking the ‘Military’ options in the Research Tree, you’ll unlock new weapons such as Sub-machine Guns, Shotguns, Grenades and even Atomic Bombs.

In the bottom right hand corner of the screen, place your weapons in the top slots, and the correct ammunition type in the slot below. If you don’t have ammunition equipped, then you will not be able to switch between weapons.

Now to switch between weapons in Factorio, all you have to do is press ‘TAB’ on your keyboard. This is the default control, but if it doesn’t work, you will need to go into your control settings. When you switch between weapons, you will see the weapon that’s colored green switch too.