Never answer when sleep deprived...
... and never answer when thinking about another thread.
Sorry, in this context, raimius, Crow Hunter, and moxie are all correct, "tap" is positively seating the magazine.
In a discussion of a specific pistol that I own, I had mentioned having to tap the back of the slide on the last round a few times, and my mind had wandered to that discussion.
Realized it after going to bed last night, and thought, "well, somebody will correct it..."