I think that we all must remember that there is a way to "Legally" attach a butt stock to even a 4" Luger. It will cost you to do it, but if you live in a state that allows SBR's (Short barreled rifles) you can file a Form 1 with the NFA branch. After approval you can attach the stock to the registered gun regardless of barrel length. Of course for this privilege you will have to pay $200.
Another way is to install a 16â? or longer barrel. There are conversion kits for the 1911-A1 that do the same thing.