Lack of practice with the rifle seems to be a real problem. When I go to bear camp, I play a game where I try to guess who will score and who won't based on their familiarity with their firearms. Pretty accurate metric.
We had two 20-somethings at camp one year who brought AR-10s. Nothing wrong with that, except that their rifles were owned by their father - they had NEVER fired them. Needless to say, both came up empty.
Admittedly, I need to fight my own temptation to upgrade my equipment. Need to put the new rifles on hold for a while.