Several years ago I had a Weatherby Orion 12 Gauge Over/Under 2 3/4".
I had some low brass and some 2 3/4" magnums and went down in my woods. I shot something with the low brass, then said "oh, that was nothing."
So, I loaded two magnum loads. A crow was flying over and at 12:00 High, I pulled the trigger. BIG MISTAKE! I was going backwards, losing my balance. The gun recoiled back, and then just as it started coming forward after the recoil, my finger must have touched the trigger and nearly instantaneously, the second barrel went off. I just about landed on my rear.
I thought "MAN, THOSE MAGNUMS SURE ARE POWERFUL, I'll NEVER shoot them again. Then I broke open the gun and saw that both magnums fired! I thought there must be something wrong with the gun!
Then I got to thinking about how the gun was just coming forward from the recoil and my finger was still resting on the trigger, so naturally I pulled the trigger a second time, all within a fraction of a second of the first shot! It literally sounded like one big bang, not two separate bangs!
I came out of the woods, and my neighbor across the street asked if that was me, and when I told him about both barrels going off, he said the sound was kind of odd.
Traded that gun last year and don't miss it.
Oh, and yes, I did land the crow and it was crow season.