there is quite a distinction between pure mathematics and actuarial studies. Actuaries tend to use mathematical results, rather than being interested in derivation, etc. Also, it's considerably more stats than maths.
Also getting a degree wont make you an actuary - its a long process, at the minimum 6 years (assuming you get all the passes/credits you need to first time round).
Check out acst.mq.edu.au and the Institute of Actuaries of Australia website, specifically Part I, II, Aand III accreditation and what exactly they are.