Alan

We are all being anal in this.

It is probably impossible to have a group from each barrel stay parallel to 300 or 500 yards. As was just pointed out each barrel group expands also thus overlapping the other barrel group. The centres may stay the same but what the hay.

I'm perfectly content with this load.

At 140m these bullets would be reversed and at 210m the spread would be crossed but still within 1 inch. Isn't that really good enough?