Sabourin: I recently got a .40 Shield and mine requires an extra bit of force to click a full 7rd mag into place. I'm wondering if it's common in newer guns as some of the mags for my Glock 23 also need some extra encouragement to seat securely at times.
The springs, when new, are very stiff. When fully loaded, how hard is it for you to push the top round down farther than the rear cut-out in the mag? Probably very hard. That, in effect, is what's happening whenever a full mag is inserted when the slide is closed.
The bottom of the slide actually pushes the top round downward into the mag (about the distance of the rear cut-out at the top of the mag), so there's going to be more resistance in seating a full mag than if it were empty, or '1 down' (not topped off after chambering the 1st round).
The spring should loosen up a bit with 'exercise'. Mine got easier to seat after a few Months.
Hope that made sense.
Yes it can be tuff when the slide is closed. Either leave it open and insert mag then chamber one or if your carrying plus one after youve chambered then youll need to influence it a little more with a solid slap on the butt to get it to go all the way home. Nothing wrong with your gun or magazine just the compression of the spring.