[Latvian291]

First response: the minimum length for a non-restricted firearm, while remaining operational, is 26 inches or 660mm (with the minimum barrel length being around 470mm). My project will be legal and I have never had the intention of breaking any law. If I did shorten it beyond this length it would still not be illegal, merely requiring re-registration as a restricted firearm which I am also liscenced to possess.

Second respsonse: My project requires no "gunsmithing" merely a custom stock (which anyone can install themselves). Folding and telescoping stocks are legal, the only stocks that are illegal are bullpups. An hilarious illustration of this is the Walther G22 which is non-restricted but has a prohibited stock!