okay so when I woke up I was just thinking of der riese .
i was thinking of the pack a punch
and then had an idea for 3 weapons .
here's a tut :

1 . have 5600 points.
2 . use Pack a Punch on any gun .
3 . whilst your character is clenching his fists , quickly run down off the platform and buy the Gewehr from the wall .
4 . now just take your weapon from the pack a punch .

i don't know if this works , it was just an idea .
you can try and see .
if this helped or worked , + rep and thank me .