The only thing I've found in the California regs on this is that they must be taken with a centrefire rifle using expanding or soft nose projectiles. So, theoretically, you could.
However, you can't own an M4 in California... the only way you can even own a semi auto clone is if it either uses the "bullet button", or is entirely featureless for a detached magazine rifle (no pistol grip, flash suppressor, collapsible buttstock, etc.) AND is built on an off-list lower.
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