My Broomie is a Federal Ordnance 712 purchased in the late '80's. They imported, rebarrelled, refinished and machined new receivers to make them semi-only (as the 712 Schnellfuerer was select fire) and put them in a nice leather case with accessiories.
The serial # on this one says it was built in the mid 30's IIRC and it shoots well now. But, the first range trip was anything but positive. Each shot (with very mild handloads) seemed to kick REALLY hard and the non-ergonomic grip shape didn't help much either. Plus, it regularly ejected a couple of loaded rounds with the empty upon firing!
Found the main spring had been cut or broken and a new one helped out a lot. But, it still didn't feed well unless I loaded the rounds WAY long...just barely able to chamber. The mags were originally made for 7.63 and are a bit long for the 9mm.
If I held the thing with a two handed death grip, it would get through both mags without mishap...most of the time. It assumed safe-queen duty for 10 years until I found some Internet articles on the C-96 that opened my eyes to what was going on.
The hammer, which looks WAY too big compared to modern pistols, plays a much more important duty than just igniting the cartridge. It's mass and heavy spring are very important in holding the action closed during firing. My hammer spring turned out to be very weak and a complete set of new springs from GunParts completely changed the gun.
It now fires standard pressure ammo with very mild felt recoil and near 100% reliability! So, if you plan on getting a C-96 and actually shooting it (much recommended!) I would advise a freshening of all the springs before firing the first shot.