Oh, a 'bump-fire'. I have gotten one double-fire like that on a Taurus 24/7 .45. The trigger is very light and apparently I put pressure on it during the recoil cycle as the muzzle was returning to the sightline. I've been meaning to take that one out and try to reproduce how I did it and learn to do good 'doubles'. All I can say is to concentrate on holding the trigger back and don't let off for the re-set until the shot is over. You may have a bit of a 'hair trigger' there that you just need to get used-to.