California laws concern 'assault rifles' are up in the air and will be for some time. If the state has its way they will be illegal to own. Court battles will be long and costly. Judges may, or may not, issue stays keeping the laws from taking effect. If the laws are overturned the legislature will enact new ones and the game starts all over again. Lather, rinse, repeat. If you don't already own one... forget about it for five years, or so (maybe forever).
Get yourself a quality bolt action rifle (Winchester Model 70, Browning X-Bolt, Remington Model 700, Savage Model 110, etc.), put a quality scope on it and practice, practice, practice. Then, practice some more. Those 300 - 600 yard shots are easy to talk about but considerably more difficult to accomplish.