I agree except on the difference between the revolver and the auto pistol. If you lay a ruler across the sights of, say, a Model 10 revolver, you will see that the barrel is pointing down from the line of sight. If the shooter aims at a target at his own eye level, he hits the target because as the bullet moves down the barrel, the recoil causes the muzzle to rise until at bullet exit the barrel is horizontal, pointing at the target.
The same is true of the auto pistol. The slide masks it, but the barrel of an M1911 pistol is pointing downward just like the revolver. When the bullet begins to move, the barrel and slide are locked together and recoil together. As the bullet moves down the barrel, the barrel and slide recoil upward until at bullet exit the barrel is pointing at the target. Not because the barrel has begun to drop in relation to the slide but because the barrel and slide have moved to a horizontal position.
In fact, the barrel will not unlock from the slide until long after (relatively speaking) the bullet has left the barrel. That is the whole idea of a locked breech pistol, that the barrel and slide are locked together until the bullet exits and the pressure drops.
Here is an x-ray photo of an M1911 pistol being fired. The bullet is almost at the exit point, yet the barrel is still locked to the slide and the unlocking movement has just begun. So the slide impacting the frame has no effect at all on the position of the gun at bullet exit.
http://www.google.com/imgres?imgurl=...9QEwAg&dur=364
Jim