The Ostian Repeaters are one of the only ranged weapons in Dauntless. However, getting the guns requires that you play the game a bit before they unlock. You will get them fairly early on after a brief bit of tutorial section in the game that shows you how to play with the melee combat items.
The Repeater Guns will be unlocked by visiting Janek Zai. He’s a weapon smith that is located in the south east side of the Ramsgate town area. He’s pretty hard to miss if you are looking for the repeater guns as the banner above his shop has two crossed pistols. Once a yellow exclamation point is above Janek Zai you will unlock the Repeater Guns in Dauntless.
Look for this NPC to get the Repeater Guns in Dauntless
However, you will need to equip the items to actually use them. You can do this by entering the pause menu and then going to loadout. Once in the loadout screen simply hover over your weapon and press the X/A button to select it. Press it a second time and it will show you the modifcations. Press it a third time and another menu will appear that allows you to switch to different weapons.
The Repeaters are on the far right of this mini-menu and can be selected by pressing the R1/RB button. Your loadout can be switch at any time up to the moments before you go out on a Hunt. Once you’re in a hunt you’ll need to complete the mission or abandon it before you can change your loadout.
Changing weapons is kind of hidden in the menus in Dauntless
The Ostian Repeaters that you get from Janek Zai are a ranged attack weapon which deal more or less damage depending on how far you are away from the enemy. They do allow you to keep your distance but aren’t quite as powerful as up close melee attacks. Like other weapons, the Repeaters have numerous modifications that can be used, which includes barrel, chamber, grip, mods, prisms, and cells which can change the power and perks of the weapon.