A lot of things happen when the gas block moves even slightly. The alignment with the gas key on the bolt causing it to wear out at an angle,the pressure loss at not striking straight on. Also the off angle that is put on the bolt carrier that will cause early and uneven wear on the inside of your upper receiver. I would never go with a set screw type, IMO it's a cop out and an easy out for a half assed way to do a job.:eek:

