http://findarticles.com/p/articles/mi_m0816/is_5_16/ai_65537472/
"Many parents, police officers, and others believe that young children aren't strong enough to pull the trigger on most guns. A recent study found this isn't true.
Almost 25% of children three- to four-years-old have the two-finger strength required to pull the trigger on most commercially available firearms. Seventy percent of children five- to six-years-old and 90% of children seven- to eight-years-old had the finger strength to pull a trigger set at 10 pounds or more. Over 90% of guns have a trigger-pull setting of 10 pounds or less."