In the build section a post was made about adding accessories to a Ruger 10/22 such as a folding stock, high cap magazines, etc. I know high cap magazines are ok to use as long as they're pre ban, but what are the legalities of adding a side folding stock to a Ruger 10/22? Does the rifle have to be made before 10/98 to be able to add one legally or is the addition of one prohibited under Mass laws no matter what?