Do you mean measuring the groups of each barrel individually? If so I'd say as accurate (or unaccurate) as any single barreled rifle. I've done some handloads with a 9.3x74r that has single barrel groups that touch all three shots at 50 yards. Now getting the composite groups is the sticky wicket. Many times what might be the most accurate load in a single barrels will not be the most accurate in the other barrel, or for the composite group. Trial and error...