Exam is worth 50% and SACS are worth 50%. I would probably be ranked average in a strong cohort (I was first until my teacher purposefully f'd me). If I was to get full marks on my exam which I can see happening if it was like last year, do you automatically get a 50? That is what people at my school say because they all think I can do it but I don't really believe it.
Legal, or most writing subjects, is so subjective especially at the top end. No one can be sure that they can full mark the exam and full marking the Legal Studies exam (or most writing-based subject) is almost like a lottery.
To give you an idea on how subjective it is, I got a statement of marks last year. Of the 4 marks (or 8 marks if you double it across two assessors) I lost, none of two assessor 'agreed' on it. That is, I only lost 1 mark max for each question so for every question that I lost marks on, one assessor gave me full mark and one took one mark off.
For now, just focus on improving your content, improving how you phrase your questions, do as many practice questions and worry about "full marking the exam" once you have done all the basics. Because let's face it, most capable student think they can full mark the exam but only the lucky one or two actually do.
But yeah, if you happen to be lucky enough to full mark the exam you will get a 50 unless your SAC rank is ridiculously low!