Loaders are a kind of small boxes in which you can carry a large amount of ammunition for a particular weapon. You can create them at the gunsmith’s workbench. Their mechanics are similar to firearms, and by pressing the R key, you can load them, causing the ammunition you had in your inventory to be loaded into the magazine. Now, by right-clicking the mouse button, ammunition will be unpacked one at a time, unless you right-click while crouching, in which case the amount of ammunition that corresponds to the magazine capacity of the specific weapon will be ejected. For example, for a rifle with a magazine that holds 30 rounds, 30 pieces of ammunition will be ejected. There is also a second way to use the loader by placing it in your off-hand. This will cause your weapon to automatically take ammunition, and you won’t have to do anything with the loader
Remember that if you use a loader in your off hand, your weapon takes twice as long to reload
The exception is the minigun loader, which serves solely for storing ammunition. Holding it in your off-hand will not cause the minigun to use it