The current reloading system needs improving, especially to give having a snaploader or clip a proper purpose.

1.) Single round reloading of magazines, whether internal or external (or putting rounds in clips)
I don't like how you can add 30 rounds in a half a second into a magazine. It should be an animation loop

• Fumble in pocket, while holding magazine IN HANDS (not in inventory. You have to HOLD the magazine or gun in your hands)
• Add a round to magazine or gun
• Repeat until "Cancel current action" or magazine or gun full
• Chamber round (in case carrying a gun) or put magazine back in pocket or backpack (in case magazine)

This makes it sensible to actually carry more than two magazines.

2.) Snaploaders and clips
I know the advantage is you can reload from inside the game without going into inventory. But I think that there should be a better solution.
A) Do NOT have a snaploader:
pressing R causes your character to open the shotgun, fumble around in pockets, then put a single round into the barrel, then a second one. Then he closes the shotgun.
B) Have a snaploader:
Character opens shotgun, snaps the loader in and the closes it
Four times as fast as A)

Same can be implemented for clips. A stripper clip should just be click, strrrrrip, clunk, tchak, loaded. If you don't have a stripper clip, see point 1

3.) Wearing working gloves should slow down manual reloading by factor 1.3 - if the game ever gets military gloves factor can be reduced to 1.1. Being COLD or FREEZING should slow down reloading by factor 1.1 to 1.3 additionally

4.) You should be able to add single rounds to the Repeater, Blaze or all shotguns, but also SKS and Mosin (any gun with integrated magazine). Drag ammo onto chambered round(s) and get context menu ("add round to double-barrel shotgun")
In the case of mosin, you should add the same animation cycle "repeat until "Cancel current action" or magazine or gun full" as mentioned in point 1