for a good shooter that is below what you can get,
you need to look for a 3.5 to 4 foot group.
i have seen as good as 16 inchs. at 200 yards,
weight of balls mic the balls for roundness, and grease the balls, or change over to turned aluminum bolts, if you can pay for them or make them, but you are doing good if you are on your own.
rick bryan