Compared this Roberts Bore Gauge to the Galazan three probe set up (which arguably works the best when used by those very familiar with it) as well as the standard Clymer (tuning fork) and probe bore gauge (such as this at Champlin Arms http://www.champlinarms.com/Default.aspx...&GunID=20). OTHER THAN REACH, we were quickly able to accurately replicate consistent readings much more easily on the Roberts. It essentially came down to how used one was to using the probe style however.