It does not appear to matter how many rounds you load, the animation and sound of rapid reload (like machine gun fire) is persistent after selecting to Load ammo.

Tested from a stack of 5, 10, 15, 20 into an unloaded Mosin.
Tested loading 2, 3, 4, 5 rounds at once from stacks of 2, 3, 4, 5.

Mosin had long range scope and bipod deployed attached, if it matters.

Hello,

Thank you for sending us your feedback regarding this issue.

Unfortunately, the problem regarding reloading the Mosin is a known issue that has previously been reported.

Closing as duplicate of #1517.

Please upvote the original issue to increase visibility and feel free to add any extra information (updated repro steps/screenshots) in the notes section.

Thanks