In other words, the sprite used to simulate reloading an MP50 or a Machine Pistol out of the 4 types currently available is MagSmall. The MagSmall sprite is also (originally) used in .45 Pistol and Pistol reloads; it is (apparently) supposed to represent a short stick pistol magazine that holds 10-12 rounds.
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Multiple weapons making use of the same magazine sprite has been a reoccurring issue for me. I have brought this up as a suggestion back in 2016 and also on the old forum, and this being an issue finally shows with the introduction of new weapons into the game.
You cannot keep using the same magazine sprite for all the weapons. It's lazy and it looks out of place. Each weapon should have its own sprite, even if they're duplicates. Each weapon should have a pointer to its magazine sprite file in a similar fashion to the method being used today with multiple weapons. That way if people modify a weapon texture they can also create a matching magazine texture for the custom model without having to compromise on quality.
Only 10 weapons (6 rifles, 4 handguns) require magazines. You've got 4. Just implement a MagStick sprite and duplicate MagAssaultRifle / MagSmall for the other weapons to make things convenient for all texture creators out there, myself included.