There is no caliber limit; except the federal one which makes above .50 caliber a Destructive Device unless the mfg has a waiver.
IIRC it was 43-38-10 and that only applied to armed security guards and it's been about a decade since it was pertinent.
IIRC it was 43-38-10 and that only applied to armed security guards and it's been about a decade since it was pertinent.