They shouldn't touch at any distance. I saw a photo of a .375 H&H (Mag or Flanged, I forget which), recent regulation target from Holland & Holland. As I recall, the group was something like 1 1/2" x 1 1/4" for six shots at 50 yards or meters.

Correct me if I am wrong, but theoretically,
the perfect target group would be:

1. Zero variation between the horizontal centerlines of the target holes. Like this (O O).

2. The distance between the vertical centerlines of the holes would match the distance between the vertical centerlines of the bores at the muzzle end of the barrels.

Of course, this implies perfect regulation, perfect ammunition, and perfect shooting. That leaves me out :-).

The left barrel should hit to the left of the point of aim and the right barrel to the right of the point of aim.

If you don't cant the rifle, jerk the trigger, etc., one barrel should not shoot above another, but there should be a bit of distance between the holes horizontally.

Measure the thickness between the inner walls of your barrels at the muzzle and add the bore diameter. If your target holes are less than this, you are crossing. If the holes are further apart, you are spreading.

However, with both vertical and horizontal impact dispersion, don't approach it as would a benchrest shooter, these are hunting rifles.