Rifle barrel length requirements are the same as federal (16" minimum length) However, what is more likely to be the problem for you is California's "Assault Weapon" laws. In our wonderful state, its also possible for any firearm you own to be an AW, so be sure to follow these 3 flowcharts for Shotguns, Handguns and Rifles.
CA has a method for allowing military members who are transferred to CA on orders to obtain a Military Assault Weapon Permit (MAWP) This process has recently been changed by our new Attorney General of CA ... Jerry Brown used to issue these without question when he was AG, but Kamela doesn't - read up about them here
If you get transferred to CA and you love the outdoors, this is a wonderful place to be (despite our byzantine gun laws)
Thank you for your service!