Yes, ammo is sold on your licence number so its recorded, not that anyone monitors usage. If you purchase regularly you can stockpile. Reloading is also an option. 9mm and pump action is plenty good for CQ. Although a 5.56 semi with high cap mag would really be nice.
Since 9mm is available, you should check out FOSSCAD. There are also many DIY smg designs that are dead simple and use 9mm.
There is also work being done on home manufacture of barrels using 3D printed tooling and an electrochemical machining(ECM) processes. In the next year or so I believe work is beginning in earnest on an open-source set of plans for a semi-auto 5.56 using the same tech. Essentially, ECM allows machining of steel and other hard metals with a non-wearing, low power process. It can be fairly slow, but it would allow the home hobbyist to machine steel to super tight tolerances.
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