Can anyone enlighten me about this requirement?

The sort of thing I need to know is:
1. How do you apply for tags?
2. What's the criteria for getting them?
3. What are the limits?
4. Anything else I should know?

I have 200 acres about 15 km out of Narrogin and rifles in .22 RF. .310 Cadet, .32-20, .357 Mag and .30-30. Am I legal using the .357? Presumably the .30-30 is a goer.

30/30 is enough gun,357 im not sure about,but the accuracy would be the number one priority.head shots only.

The 30-30 will definately make the grade.
The 357 would need to be stoked to absolute maximum and even then I dont know if you would get the required muzzle energy and as wharf said, you need enough accuracy for a brain shot.
As for the tags, you need to be a commercial shooter or find a property owner who has destruction tags.
I believe that if you shoot them on destruction tags you are not allowed to harvest any part of what you shoot, even for personal use, someone can correct me if im wrong on that one.

As far as I know tags are for commercial shooters.
Roos taken on damage permits are under the drop and rot scheme. Some shires have an open season but most that run under damage permits a property owner has to prove excess numbers and genuine damage.

I think you still need tags mate