I would suggest that while heavier bullets generally tend to cause the barrels to shoot further apart than lighter bullets, there are exceptions. For reasons I cannot explain, my German .250-3000 double rifle shoots the 87 grain bullets further apart than the 100 grain bullets and regulates at about a 1-1/2 inch spread at 100 yards with 115 grain bullets. No, the lighter bullets are not cross firing. I checked that.
As I said, I can't explain it, but that's the way this particular double rifle performs.
