IN DEFENSE of sir Ricciardelli, I must chime in and say that recoil as a measurable effect upon barrel alignment typically does not begin until the bullet begins to move. Hammer fall and primer popping just don't move things much.
But Mr. R. is right about the Python's designers being amazingly prescient in giving it such a short front sight that most loads heavier than 125-gr strike noticeably above point of aim. Fooeey! Badger--sure a previous owner didn't mess with the front sight and shorten it? Or did someone put those nasty Millet adjustable sights on? You know, the ones that stick way up and deprive you of maybe six clicks from the bottom of the OEM adjustable sights' range of movement?
If you're shooting 158s at .38 Special velocities, consider this: the heavy weight and long barrel time make such loads strike about 3 inches higher at 75 feet, compared to Magnums.