As the title says, while firing with the "AKM", which is available with the Insurgents, there is no shooting audio. However, hit sounds are available, so only firing it is muted.
No Shooting Sound using the "AKM"
That's a sound bug, it doesn't always happen but can do occasionally, and can happen to pretty much any weapon, it usually will go away at some point and in your next game, it will be fine, don't worry.
Did this always occur for you or did it happen after the hotix? I'd suggest verifying the game cache to ensure the game doesn't have any missing files.
https://support.steampowered.com/kb_article.php?ref=2037-QEUH-3335
@Captain-Price i didn't have the game before the Hotfix, just bought it same day i posted this.