Before the 2014 Love & War patch (or maybe the 2013 Two Cities patch), the Tomislav used to have higher pitched sounds for firing and deploying. The sounds changed because the pitch ended up getting controlled by the 20% slower firing speed.
This video (Watch on YouTube demonstrates the incorrect firing sounds, and shows a fixed up version of how the Tomislav is supposed to actually sound like.
If you have ever wondered why the ammo drain doesn't seem to sync up with the firing sound while firing the Tomislav, this is one reason why.