John: I think Jack might be correct only because that is the way the Eyster's who have been competition choking shotguns for years do just that. Normally, they have the shooter shoot their gun free hand. And when checking point of impact, they have the shooter shoot a 5-shot group and where the pattern is most dense is that spot of POI. All this is done free-hand. When assessing the pattern itself and rechoking of the gun, single shots are taken with the shell one intends to use in the gun. For example, I had a Browning Superposed 20 bore choked for grouse hunting with Remington Express #7 1/2 shot. As a result of Ken Eyster's (he is now deceased) work, this Browning throws superior patterns with Remington Express at 25 yds for bottom barrel and 30 yds for the top barrel. This is the method they use for all their competition choking of shotguns and they never use a bench rest. Also, they have you shoot your gun on water in assessing poi. I have found Shooting at an object on water useful in assessing where a gun shoots for me. As in all things, there are many ways to skin a cat, but I think the way the Eyster's do it is pretty scientific and effective.
