Sorry, but that is a myth. Several shooters have shown that even with the Mannlicher-Caracano three accurate shots could be made. The fact that two struck JFK out of three is the proof. The first shot hit a traffic signal and working the bolt of this gun is quite smooth.
You are correct. Been to the Book Depository, seen the angles and measured the speed of the presidential vehicle. There is no doubt Oswald had the angle and the time given the slow speed of the president’s vehicle. Oswald had a clear shot and was a marksman.
I once was a conspiracy believer. After having been there and seen the site, I believe Oswald could and did commit the assassination himself.
What is remarkable and eerie to me is that after nearly a half century, the site at Dealey Plaza is remarkably close to as it was is on that horrific day. Going there and seeing it for the first time last year felt like walking on a movie set. The buildings and atmosphere at the scene feel like you are stepping in a time machine back to 1963. It is very emotional to go there and see it for yourself. It is worth a visit for one to go and see it personally.