They defintiely wouldnt mute rage. But they do help other aspects. For example, i did and soemtiems still do snap without warning, vie been known to throw things around, shout, and scream, despite being a totally non violent person, it happens before i even know whats happening. Beta blockers pretty much put a stop to this. You just dont get that "rush" (but not the good kind) when something happens that makes you angry or scared.
And however mentally stable you feel you are, it really is best to see a professional. Im not a doctor, but more than likely something in your life past or present is causing this, Or perhaps (dare i say it) cannabis has had a role in it. Im open minded on the effects of cannabis, but I have seen mental illness worsened by cannabis with my very own eyes.
Please see a doctor, the way you feel now isnt how it should be, at the very least they will help you get a grip on it when it happens, and put you back in control of your emotions. Nobodys born angry.