30.06 rifle. That's pronounced a "thirty aught six", the most famous being the Springfield. The specs for the cartridge for it are 7.62 x 63 mm. And the Carcano attributed to Oswald used 6.5 x 52 mm.
So, you consider that and the fact that the only witness, Walker's neighbor, said it involved two men (Oswald had no friends) and two cars (Oswald had no car, no license, and no ability to drive), and thus you realize that there is no evidence whatsoever pointing to Oswald. The ONLY thing pointing to him was the flapping lips of his wife.
I will tell you here and now that the transformation of Marina Oswald into the talking puppet of her FBI/SS handlers has got to be one of the most dramatic, incredible, and speediest brainwashings to ever occur in the history of brainwashing. And, it's scary. The monstrous things she said about her own husband- it was like she became a totally different person.
And realize that she was living in a world that was DEVOID of Oswald supporters. There was NO ONE. The only possible ones would have been her Russian family and friends- back in Russia. And, as I said, I strongly suspect they kept her from receiving any mail from them. Think about it: if they were planting all these ideas in her head, and then she got a letter from a close, familiar person saying, "I don't believe for a second that Alec could have done this. No way! And you know it too." They were making statements like that even decades later. So, consider how disruptive it would have been if she received such letters while she was being programmed and installed with new memories.
Here is an article the UK's Daily Mail which says that at the time of the 50th, Marina Oswald turned down $3 million to talk about the assassination.