Even if it could be proven that Oswald owned the C2766 Mannlicher Carcano rifle (and it cannot) and if it could be proven that the C2766 Mannlicher Carcano rifle was the assassination weapon (and it cannot), it doesn't just follow that it was Oswald who fired it.
Ignoring your "assertions" about non-ownership of the rifle (C2766) by Lee Harvey Oswald: It's
probable that the owner/possessor of the assassination weapon was the assassin. With no physical evidence of another (or if it pleases you... alternative) assassination weapon: It's
probable that Lee Harvey Oswald is the assassin of President John F. Kennedy.
It "follows" that the shots attributed to the sole assassin were
possible... because we have no physical evidence of any other weapon (or bullets fired from it).
Reconstructions by experts who do not believe Oswald is the assassin are suspect because "failure" can be intentionally achieved to suit a predetermined "negative" outcome.
Alternately, reconstructions by a believer in Oswald's guilt entails striving for "success". A deliberately sub-standard performance will prove them wrong.
Of course, it's
possible that a believer in Oswald's innocence might pose as an impartial "seeker of truth" and influence the reconstruction accordingly.
As you know John: To a believer in a conspiracy to assassinate President Kennedy... anything is
possible.