I have been playing Titleist CB irons for several years.  I recently picked up a set of 718 AP2 irons to demo.  Since I am not able to practice as much I figure I could use a bit of technology help.  The AP2s have a KBS Tour 105 shafts.  This is the same shaft I have played in my CBs for the last 3 years.  I have looked at measured head weights only for both the CBs and AP2s and there is minimal difference.  When I got a chance to actually lay my hands on the AP2s they immediately felt heavier....and not just a bit.  The difference in weight was noticeable throughout my swing.  The only difference in the clubs other than the head is I play my CBs -1.4" and choking down a bit on the AP2s did not reduce the "heaviness" at all.   Distance, feel, dispersion were all good.  
Ideas?