If you wish to own a firearm the reasons for it are 1. For your profession, some security agencies for example 2. Sporting purposes 3. Hunting 4. Collecting
Those are the main reasons to own a firearm.
You can buy ANYTHING YOU LIKE, as long as it is suitable for the purpose, ie a 9mm or bigger for IPSC and 3 Gun matches and a semiauto rifleto the previous ones also. I personally own a Busmaster M4A3 flattop carbine, L1A1 made in Australia and a HK USP in 9mm. I bought my first weapon when i was 15.
If you wish to start collecting any weapons for example you have get yourself approved as a weapons collector with the state officials.
Basically when you feel you´ve been around weapons and owned them long enough you send them an applications stating why you want to collect(technical details, historic value, etc..), weapons from what era, how many, timeframe(can be very wide), list where you have gained knowledge of weaponry and such things. If they approve you, then you CAN BUY WHATEVER IS ON YOUR LIST, including M203s even.
The line with the officials has tightened somewhat but a with reasonable efforts you will get approved. And our prices are ridicolous compared to the prices you have to pay in the States for HK94 convert to MP5s for example