Accuracy can be greatly affected by throat erosion. Quickly and easily check the wear of your service rifle throat with this simple tool. The gauge simply slides into the chamber and a reading is taken at the rear of the barrel. New barrels should register at zero, while barrels too worn for service use will register past the last mark.
The gauge is used to see the relative change in a chamber's throat by measuring the throat when the rifle is new or when gauge is first used, then comparing later readings with the first reading taken, noting how many rounds have been fired from one reading to the next.
The Gauge Spacer is used with the M1-type gauge. The spacer inserts over the M-1 gauge for the corresponding other rifle listed in the description.
The M1, M1A gauge will work with many short action .308 caliber rifles.
The 224 diameter gauge is used alone in any 22 caliber centerfire rifle where access to the breech is possible.
The end of the gauge (or the spacer) that is inserted into the chamber has a series of lines on it. By noting how far the gauge can be inserted, one of the lines can be used as an index, or starting, line. Subsequent uses of the gauge and the corresponding line that can be seen when the gauge is inserted will give a difference in dimension between the two lines. If this difference is then measured (with a dial caliper or other measuring device), the result is the amount of throat erosion that has occurred.