I had to DQ a shooter today at our local IDPA/DMG monthly match. I think it hurt my feelings more than his because I consider him a good friend.
Short version is, during an adaptation of one of the stages, in which we were using carbines from either side of a Bianchi style barricade, he put a round through the barricade from a distance of about 3". He was shooting one of the Beretta 9mm carbines with a red dot on top, and didn't take into account the distance from the muzzle to the center of his optic as he sliced the pie. In addition to that, he made the decision to shoot left handed around the left side of the barricade, and is right hand dominant.
A word of warning to RO's, SO's and trainers. I haven't seen this happen in quite some time and never from that close. Fortunatley is was ball ammo and thin plywood.
Wheeler