What about the 5-shot clip?
How did Weitzman know how many rounds it held? Was it:
a) Once he decided it was a Mauser, said it was 5 because Mausers hold 5 rounds?
b) happened to be carrying several rounds of Mauser ammo, and started loading them into the weapon just to see how many fit?
c) picked up the rifle and unloaded five rounds from the magazine?
If you want to argue b) or c), you'd better have a damn good reason to claim either.