Get a firearm.
Hold it in your hands
Make sure you shoot a few rounds so the magazine isn't full.
press R (or any other assigned...Duh) to reload.
Nothing.

This should be a major concern as reloading via the inventory screen is a giant disadvantage in the middle of a firefight.
Suggestion with how weapons should work:

Double-barreled shotgun: when empty, the server checks if I have any correct ammo left, if yes, plays either single or both shells reload animation (or with snap loader). This should also allow to reload a single round, if one shot was used. (SUPER annoying to be force to empty the gun and the reload it again THIS is also with the Mosin and all the magazines)

SKS Simonov: Either does a full magazine reload or adds few rounds to the gun to fill it.

Mosin: only plays the animation loop (single round in the gun) so many times, how much bullets are needed in the gun (for example, if I have three left, the animation loops 2x to reload to bullets)

M4: Changes the current magazine with any other magazine available that has the most bullets. If all magazines are empty, filling them has to be done manually.

Semi automatic pistols: same as the M4. PS: if there is no magazine available, it will chamber the gun if enough ammo is in inventory. This should work with any weapon.

Revolver: Just a normal reload if ammo is available