Owning a pistol and a shoulder stock that can be attached where the barrel is less than 16 inches and the length of the firearm is less than 26 inches is a violation of the NFA without an approved Form 1.
There are certain exceptions for some items which have been removed from the NFA under C&R such as an original and unmodified Mauser “Broomhandle” and some Lugers. Remember that the NFA use to permit modification to C&R but no longer does. If you have a gun that was C&R and then modified, it most likely does not maintain the C&R status of the firearm.
This was common in California and if you are in possession of these items, it is our belief that you are no longer permitted to be in possession and you should check with the lawyers we work with in California understand your rights and obligations.