The M82 rifle itself will shoot bullets in a 20" spread at that distance, even if the rifle was set in concrete , fixated on the exact same target point each time the trigger was pulled. So even if everything were calculated perfectly, that rifle could shoot the 10 rounds spread across the 20" grouping/spread, and there will be several clean areas within that spread where a 6" circular target might fit, and thus not be hit.

And to even have a chance at getting the 6" circle within that 20" spread range (and you must reset the rifle on that exact target point again every single time, due to recoil), you have to be correct on calculations for at least all of the following:

Bullet drop, Wind drift, Elevation, Inclination, Rifle Cant, Barometric Pressure, Air Temperature, Humidity, Coriolis Effect, Spin Drift, Magnus Effect, etc.

It's a crazy difficult task.