Maybe this will help HopDoc,

Your rifle, properly loaded for, should shoot a right and left with the inside edge of the two bullet holes in the target only the disance apart that the barrels are seperated at the muzzles. Maybe a a quarter to a half an inch.

If you shoot at, say, 5yds the edges of the bullet holes are as far apart as they are a 10yd or 20yds or...til the finaly drop enough to hit the dirt.

This example assumes the perfect regulating load from the perfect shooting rifle, but you should get the drift. Properly done, you rifle shoots the barrels parrallel, as has been pointed out.

To make sure your load is just right you need to shoot at 25yds, 50yds, 100yds and further if your range allows. The right and left barrel group centers should be the same at all ranges.

For me this is theory, though I think I've gotten it right in my rifle. I just can't see with the open sights well enough to shoot well enough discern whether there is any convergence or divergence at 100yds. On a light rifle, with a scope it would be easier.

JPK