Cause of slam-fire in my 6.5CM AR10?

[montana]

I personally suspect about half of the slam-fires that occur, are actually trigger discharges for one reason (it got bumped) or another (tolerances/excessively light trigger).

This is what happened to my M1A1. I got double taps thinking it was a defective trigger. After careful testing, it was the light trigger getting bumped during recoil.