Good video, found a bug:

You reload red bullets - the weapon throw out green bullets instead red.

You should add this to your post heading to fix the bug in the same moment .

Hey @Geez on a further note, this can also be reproduced after sprinting, coming to a jog to try and reload from the hotbar or Press 'R' to rack the gun.

Disclamer the encoding got overloaded so the footage is laggy D:

but basically, I was trying to load the gun or press R as soon as I came to a jog from the sprint, but I was getting the issue as above since I was going to instant sprint right after.

To Reproduce when loading ammo, or racking the gun:

1. Sprint
2. Come to a jog, try to reload bullets on hotbar / press R
3. Instantly try to sprint after doing so.

Good Solution
If the player attempts to reload from the hotbar during a sprint
or press R in Sprint

The player will automatically be forced by the game to come to a jog, to perform this User Action by default, to increase the fluidity and responsiveness of combat :)

Once it's done they can sprint away or cancel it with sprinting away if need be?

The fact that you can´t cock, reload or change mags of a gun while running its something thats definetly need to change. At first I thought like the OP it was a responsive issue but its not. Then many thought it was a design decision, and its not
The issue is in the action you perform first:

• If you start running before you hit the "R" key -> You wont be able to cock/reload/change mags of your gun until you jog
• If you hit "R" before you start running -> You can actually run and reload without any issue.

This issue have a huge impact on pvp and makes people question the game keys responsiveness.