AR15 CMMG .22 Upper

[Quiet]

you wouldn't catch me with one of the listed name lowers with a 22lr upper

There is no rimfire exemption to CA make/model banned assault weapons.

[Quiet]

Do rim fire AR pistols have to be break open action/fixed mag ?

Rimfire pistols are not exempt from CA assault weapons laws for pistols.

A semi-auto rimfire pistol that does not have a fixed magazine and has restricted features is considered an assault weapon. [PC 30315(a)(4)]

Restricted features on semi-auto rimfire pistols that do not have a fixed 10 or less round magazine:
1. Threaded barrel.
2. Second handgrip.
3. Shroud.
4. Accepts detachable magazines outside of the pistol's grip.

Semi-auto rimfire pistol that have a fixed magazine with a capacity of greater than 10 rounds is considered an assault weapon. [PC 30515(a)(5)]

Fixed magazine being an ammunition feeding device that is contained in the firearm and can not be removed without disassembling the firearm's action or that is permanently attached in the firearm's magazine well.


Therefore...

Since a semi-auto rimfire AR pistol accepts magazines outside of it's grip, it must utilize a fixed 10 or less round magazine to be CA legal.