Oswald in the doorway: the blog of the Oswald Innocence Campaign, by Ralph Cinque

This is by Craig Roberts, the former military and police sniper who is a member of the OIC. He is also the author of Kill Zone. 

"Now, to the point:  Who really shot Tippit?  The shell casings found at the scene were from a .38 Super (a very popular police and CIA pistol at the time). The .38 Super is a Colt 1911 Semi-auto!  These are rimless cartridges that will NOT work in a .38 revolver!  Get it?  Oswald's revolver could not have been used to shoot Tippit.  The casings were found because they were ejected from the semi-auto, and a revolver does not eject it’s spent brass.  So, the gov’t lied again.  And no one, not even Dallas PD, followed up on this. And if I remember correctly, the revolver Oswald had had a broken firing pin and could not fire. "

So, the pistol on Harvey could not have been the gun that killed Tippit.