I "borrowed" this image from M2 Carbine (in another thread). Nice tight group out of that shotgun! Much tighter than I would have thought (tight choke? Ammo?). I've attached four images from a pattern test done at the NYPD (by me), showing the difference between full and open choke group size using 00 buckshot.
As you can see, sights are really needed to ensure hits when using a shotgun, just as with any other firearm.
Full Choke 00 Buck 25 yards
Open Choke 00 Buck 25 yards
Open choke 7 yards 00 buck
Full choke 7 yards 00 buck
As you can see, sights are really needed to ensure hits when using a shotgun, just as with any other firearm.
Full Choke 00 Buck 25 yards

Open Choke 00 Buck 25 yards

Open choke 7 yards 00 buck

Full choke 7 yards 00 buck
