I use this caliper in conjunction with the Hornady Rimfire Thickness Gauge to identify .22 caliber rimfire ammunition that has a rim thickness significantly thicker or thinner than the "normal" I have defined for a case or carton. Ammunition. The combination has an accuracy of up to 1/100 millimeter. This allows me to easily sort out cartridges with rim thicknesses in the 3/100 millimeter range, for example, and weed out those that exceed that range, either plus or minus. You can reset to zero with peace of mind once you have determined the "normal" rim thickness. Also, it's pretty quick to spot a poorly made crate or a crate of ammo.