That would be an illegal firearm, without special paperwork, here.
A SBR, I believe.
Over here it is illegal to make an existing firearm shorter beyond a minimum length, but it is not illegal to make a firearm longer, so those Glock stocks and carbine conversions where you sort of bolt your G17 into a picatinny'ed frame are all OK to own.
When the right to effective self-defence is denied, that right to self-defence which remains is essentially symbolic.
Freedom: Please enjoy responsibly.
Any idea that relies on murder for its survival in intrinsically weak.