I would like to suggest the Rheinmetall S-18/1100 which is the 3rd Model of 20mm Prewar German AT Rifles, beeing a further modified S-18/1000 with the ability to switch the firemodi to Full Auto.
When combined with a 10 (or even 20 round) magazin and Pzgr.40 it would offer a possible BR II AT rifle.
A mounting for AA purposes also existed.
Germany, cince prohibited from any development for Wareffort, bought in the late 1920s the Solothurn company and used it as a fasade company, sending their engineers there to develop guns and ammonition in secrit.
Among the development were the 20x105mmB Rheinmetall, 20x138mmB Rheinmetall and 30x184mmB Rheinmetall ammo, as well as for a early requirement of new AT Rifles the S-18/100, later S-18/1000, as the power of the /100 was seen as insufficient.
As the German Army showed less interest for these guns, they were not fully integrated into service, beyond captured and some other exampels.
A further development was the /1100, which was a choosable Semi/full auto Version, also available with an AA mount for AA purposes.
While the S-18/100 has allready been found in the files, hopefully also a /1000 some day, a /1100 with great magazin size and Pzgr.40 would offer a good BR II All purpose gun against infantry, tanks and aircraft, duo to great velocity of 1050m/s and penetration 48mm (or if historic values 64mm) at 10m.
Otherwise the /1100 is pretty much identical to the /1000
Ammo:
Types: (not limited to, but for in game purposes shortened to) ApI-T, HVAP-T, HEF-T and HEF
Pzgr. L`Spur. o.Zerl. (Ph.) (ApI-T) 0,148kg 830m/s 40mm/10m
Note: Used against ground targets. Soft and armored. 3g White Phosphor Core.
Were fully replaced by the empty ones and later .Zerl in the Desert and other hot places, as the Phostphor had a nasty tendicy to self ignite in hot weather.
The Ph. marked ones were standart with the filler, however they also existed with an O. which indicated they didnt have a filler and were only 143g (and 835-840m/s).
(Velocity for L/55 is 800, 805-810 for the 143g.)
Some sources give also a General velocity of 800m/s (and 805-810m/s for the lighter rounds)
Pzgr.40 L`Spur. o.Zerl. (HVAP-T) 0,100kg 1050m/s 62g core 12x45mm 50mm/10m
Note: Only used against heavy armored targets, where the standart Ap ammo does not penetrate.
(There were 3-4 generations, with ever increasing length and slightly weight, to improve stability.)
Sprgr. L`Spur. m.Zerl. (Hef-T Sd.) 0,120kg 900m/s 6,2g Pent (10,54g) 5mm/10m
Sprgr. Erd. o.L'Spur. o.Zerl. (Hef) 0,120kg 900m/s 11g Pent (18,7g)
Alternative name Sprgr.39
