So, in Inquisitor, they had what were called "placed shots". DH has called shot modifiers, which covers the mechanic the Placed Shot rules were affecting (being able to adjust the location you hit). Instead, I thought it would be cool to use the same target numbers in order to do a little bit of critical damage, since the charts are awesome. I'll call them Lucky Hits.
You get a Lucky Hit if you:
Roll 1/10th or less of your to hit number. (if you need a 60 to hit, and you roll a six or less)
If you aimed, the number you are looking for is less than your to hit number, minus the range to the target. (if you need a 60 to hit, and they are 10 yards away, you need a 50 or less)
If you get a Lucky Hit, you do d5 critical damage to whatever location you hit, in addition to your normal damage.