Bad analogy. You don't train with invisible guns or iron sights nor would you pass on a virtual training that'd have live ammo and the same physics as the real thing, and a nice reset button to repeat said training scenario over and over.  Hence what I said.  There's a lead computed sight offline (might be on in the TA, I dunno), you just lock onto your target with TAB key. CTRL-TAB to toggle friendly lock on and off.