Count three seconds after the detective ( Studebaker?) lifts the camera.. and notice the metal butt plate of the rifle. Day has just grabbed the leather sling and the butt plate is HORIZONTAL.
Here are my thoughts re this sequence:
1) Day could have reached down and tipped the rifle on its side with his right hand so he could grab the strap with his left hand. Then when he lifted the rifle into view, it was horizontal. But he still had hold of the rifle with his right hand when he lifted it up then shifted it to his left hand holding it by the strap and letting go with his right hand. IOWs, the rifle could have been upright before he lifted it from the floor. But I don't think so.
2) Or when Day moved the boxes he laid down the rifle on its side 1st, then he went back to it for the "discovery scene" with Alyea filming. The photos were taken well before the boxes were moved. But when?
3) Note how Day grabs the strap which is in front of the rifle as it lays on its side. If you rotated the rifle upright the strap would still be in front of the stock and in plain view. A photo would clearly show the strap and the 2 photos taken by the DPD did not.
I believe those photos were taken well before the Big Event and were just more staged evidence to frame Oswald. It is preposterous to think that Alyea would have shot footage of the photographer taking the photos of the rifle in-situ and not shot footage of the rifle as well. I am willing to bet that Alyea actually did film the rifle in-situ but it was cut from the film when they noticed it did not match the 2 photos.
But how could the Alyea footage not match the 2 photos taken by the photographer so they would have to cut it out? The mismatch was either the footage showed the strap when the photos didn't or the footage showed a Mauser in-situ, which they had to swap out for the MC, before letting Alyea film the discovery scene. This would explain how a Mauser got into the mix, yet the Alyea film shows Day picking up an MC. But their edits render the timeline of events to horsespombleprofglidnoctobuns.
But why would they use the 2 staged photos of the strapless MC in-situ when the actual 2 pics taken would have matched the Alyea footage? Why did they decide to use the staged photos and cut the footage from the Alyea film instead? I think they were so arrogant that they went with the staged pics and later realized they didn't match the Alyea footage so by that point it was easier to cut it out of the film because they probably tossed out the actual pics taken at the scene or they might not have even had film in the camera. The fact that they only took 2 lousy pics of the murder weapon for the crime of the century is bad enough.