It’s somewhat closer to 1 in 7 million.
Figure that (angle of target gun aside) the placement grid is about a tenth of inch, and you can bring your shot to a square about 18 inches on a side — that 32,400 grid spots only one of which is good for true. That’s your odds of hitting the barrel.
To go UP the barrel you then need angular alignment, which is controlled by the target person. Figure that the target gun is being pointed at you pretty closely, so there’s a grid of maybe 15 angles up/down and 15 angles side/side only one of which is good for true. You multiple by 32,400 by 225 (15x15) to get in one in 7,290,000.