Having watched and been a top ranked long range competitor, it's interesting to watch the best do their best shooting slung up in prone. Then on their second or third day on the same 1000-yard range, set their sight to range zero for the same rifle and ammo, dope the wind then do all the thinking and calculating to take their first shot on the same firing point they used the last two days. Then click the sight knobs again for a final correction, breathe deep a few times, cut the last breath off short, aim and hold as still as they can. Their point of aim bounces around in sort of a figure 8 pattern in an area on bullseye target center about 6 to 7 inches across. That's their pulse beat their heart makes pumping blood to their vital organs. One of those organs is their eyes. Eyes maintain clear vision for 15 to 20 seconds without fresh oxygenated blood. So, the rifleman needs to get his shot off while his eyes see clear enough to aim precisely. Finally the shot fires, he calls the shot then waits over a second for the bullet to strike the target.
Maybe 5% to 10% of the best will put that first shot within 6 or 7 inches of where it was called on target in ideal conditions. The rest will often miss call further. Maybe it was because they didn't notice a slight wind change of 1 or 2 mph that causes their bullet to strike horizontally to the side 15 to 20 inches. Maybe they misjudged the wind forgetting that winds at the highest point of the trajectory often are 50% faster than in the line of sight. Maybe his position holding the rifle was not 100% the same as the average that let him shoot to point of aim; happens 90% of the time for most people.
It all boils down to the fact that while his rifle and ammo well tested kept 20 to 30 shots inside 6 inches at 1000 yards, hand held rifles fired off ones shoulder slung up in prone on add 1.5 to 2 MOA to the area bullets go into for the best of them on average. So keeping all fired shots inside 20 inches 3600 feet down range is seldom done. 25 inches is a lot more common and 30 is close to an overall average.
Watching the movie "Quigley Down Under" watching Tom Selleck showed the bad rancher his 900 yard target with a dozen or so bullet holes covering his palm to prove his skills for the job he was after made me quietly chuckle. The best 45 caliber black powder rifles in that late 1890's era used in long range competition would keep 15 shots inside about 18 inches that far down range; about 2 MOA.