What evidence is there for a second rifle being discovered?
Doesn't Weitzman's signed affidavit that he examined a Mauser on the 22nd give you the slightest bit of pause? Otherwise, why would you think he knew Mausers were 7.65 caliber and a Mauser held 5 rounds? He admitted that he was no expert. Do you really think that Weitzman was describing a rifle from another day or the MC?
If Weitzman was telling the truth (before he thought better of it) then there were 2 rifles found on the 22nd. In which case, the Mauser was not captured on film because Fritz pulled a switcheroo before Alyea started filming. Fritz seemed to be in control of what got documented and how to stage the crime scene before any film was shot. For example, Fritz tampered with the crime scene by picking up the 3 hulls with his bare hands and put them in his pocket, then later staged an in situ photograph of the hulls in a more scattered (believable) arrangement by tossing them onto the floor so a rookie cop could take a photo of them. If he could do that, then what's the big deal about pulling a switcheroo with the rifle, if he had to because a DPD bumpkin stumbled onto the Mauser by mistake?
Otherwise, you have to believe the testimony of the conspirators that the 1st rifle found was the MC. Why you and Walt believe Fritz and Day is beyond me. Screw the film. Fritz staged that too. Alyea might have been oblivious to it all, but I doubt he would have been allowed to be there if Fritz didn't have control over the narrative his film portrayed.
But since you are a LNer, you think the MC is THE 1 and only rifle, which Oswald used to kill the POTUS with a magic bullet and a wonky scope from the 6th floor of the TSBD. And definitely NOT with a Mauser! Walt thinks the whole Mauser story is insane BS but his crazy conspiracy theory is AOK.