When debating, never use negative words to describe your point of view ie. 'may not be perfect.' Your opening claim should be more along the lines of: "Gun control laws are an effective way to lower the occurrence of gun related crimes."

I would re-word your claim and data a little bit too, including grammar. to something like:
Claim: Many countries have enacted strict gun control laws that have lowered gun related violent crimes.
Data: In 1997, Australia enacted laws that made handguns illegal and seized over a half million guns. As a result, firearm related deaths dropped by 47%.
Warrant: When strictly enforced gun control laws are effective in lowering gun related violent crimes.

Try to avoid thoughts of 'i don't agree with what I'm trying to say.' Because, the professor would not have provided such a two-sided case without strong arguments on both sides. It's easy to do the research, take your time, and textually argue something you may not agree with personally. It's difficult to do it verbally - so try to psyche yourself up before presenting. I do this by convincing myself that what I am presenting is not only important, but also 100% truthful. Sometimes I lie to people, I'm human. Lying takes the same preparation.