I have shot 1 inch groups at 100 yards with a peep sight. But I cannot do it with express sights. 2-3 inches is what I get with express sights. Maybe it's just me.

At 50 yards I can shoot 2 shots an inch apart with my double. At 100 yards I have shot 2.5 to 3 inch groups per barrel, but the whole pattern does not fit into 3 inches at 100. Probably I would need to regulate the load for convergence at 100, but I probably will not do that as I could hit the heart of a buffalo at 100 yards with things as they are and that's just fine. I doubt I would ever try to shoot a buffalo at 100 yards because one of the joys of buffalo hunting is getting in close.