The stock trigger pull (you must apply this much pressure to the trigger to cause the gun to discharge) on a glock 17 is 5.5lbs and can be used by frail old people, many people even soften it to 3.5lbs for competition. The NYPD uses between 8lb and 12lb triggers to prevent accidential discharges. 3lbs would require no finger strength what so ever and would almost be unsafe.

Just may want to work on that bit

If you wanted the illusion of it being a hard to pull trigger call it the 20lb trigger and reduce accuracy to compensate from how messed up your grip will be when trying to apply 20lbs worth of force to a small metal bar