The main discrepancy between the Watson and Flashman versions is interesting rather than important: Watson says that Moran fired from the ground floor of the empty house, while Flashman places him in an upper storey. The error is probably Watson’s. There has been much controversy among Baker Street addicts about angles of fire, the laws of optics, parabolas, etc. (see Baring-Gould), but to a rifleman it is obvious that Moran would have preferred a direct horizontal shot to an upward one, and this seems to have been the opinion of the artists who illustrated Watson’s account: the celebrated Sidney Paget, in the Strand Magazine of October, 1903, shows Moran looking straight across from his window, and the drawing of the American illustrator Joseph Camana in 1947 has both marks-man and target on the same level.
Both Watson and Flashman are mistaken about Moran’s age. Watson says he was born in 1840; Flashman, by stating that Moran was fifteen years his junior, implies that the date was 1837. But since Moran himself states that he was fourteen in 1848, we must accept that he was born in 1834, which is in keeping with Watson’s description of him as "elderly" and a "fierce old man" in 1894.