I currently have a NID 4E with a single selective trigger (Miller) that occasionally doubles in the sense of firing the second barrel a split second after the first - ba-boom. It is not a double discharge in the sense of both shells firing at the same time. The gun weighs near 9# as I shoot it with a Galco pad and spacer. The offending occasion, to date, is use of 7/8 oz loads at 1100 fps. These are most likely to light in this gun to move the inertia block fully into position. The consequence is that the second, involuntary, pull ignites the second barrel; it will do it with the selector in either position. There doesn't seem to be any particular hazard to me or the gun (we are both robust to the event), but it does seem to startle the gallery. However, in a lighter gun with loads closer to the gun's power limit, this would be a problem to be dealt with forewith. The solution, in this case, is shoot more powerful shells, dink with the works, or send it to Doug Turnbull for tuning to the light load.