Nanuk, no adjustments were needed. When loading a AR15 whith the bolt open no hitting of the mag is needed. When loading an AR15 with the bolt closed a harder push may be used but again, no hitting of the mag is needed.
You are correct in that, with the bolt open the mag should easily insert. With the bolt closed a slap on the mag may help seat it. By slap I do not mean try to send it into orbit, its more like a tap. I have been using AR's for 30 years in the Military, LE, and competition. I am an AR armorer.