Some folks seem to believe that the dent in the neck of one of the spent Carcano cartridges found on the sixth floor of the TSBD indicates that it couldn’t have been fired on 11/22/63. However, there is a very reasonable explanation for the dent that has credible supporting evidence and is consistent with that cartridge being one of the three shots believed to have been fired on 11/22/63. Let’s start with an animated GIF showing slow-motion of a shell being ejected from a lever action rifle. You can see the ejected shell spin end for end and the neck end of the cartridge hit the rifle and bounce off. It appears to me that the neck end of the spent cartridge is flattened a bit by the impact.

Here is a still image from that GIF showing what appears to be a somewhat flattened neck.

I had previously posted in another thread a link to a video of a Carcano M91/38 ejecting a spent cartridge that also bounced off of the rifle at the bridge to the rear of the ejection port. Here is a still frame from that video showing the cartridge just after it bounced off the rifle.

What we cannot see in the Carcano image above is what that rear bridge looks like from the rear angle. Here’s an image from Nova’s Cold Case JFK that clearly shows the sharp edges and/or corners that could have made the dent in CE543:

The FBI duplicated the dented cartridge in their tests by cycling the Carcano’s bolt very quickly and forcefully in an effort to simulate someone trying to fire consecutive shots a quickly as possible.