Wilson 300 Blackout Case Gauge
L.E. Wilson has been making precision reloading tools for over 80 years. The Case Length Headspace Gage allows reloaders to measure case length from the base of the cartridge to the shoulder, as well as the maximum case length. This process shows the reloader if ammunition is being produced within SAAMI specifications.
Features: Precision Machining
This is a one-piece, non-adjustable cylinder-type gage for checking fired and resized cartridge cases for cone-to-head and overall length
Used to compare cartridges against the minimum SAAMI chamber dimensions
The item description will indicate if the headspace gage is Adjustable
Drop a fired case into the gage. Take a measurement on headspace. This can be done with either a depth micrometer or caliper (Depending on if the case is sitting high or low in the gage). If the case sticks out past maximum headspace the firearm probably has a larger than average chamber. The gage can still be used because it is being used to determine how much resizing is required.
Now once the initial measurement is taken, slowly dial in the full length sizer until there is a 0.001 to 0.002 drop in headspace. This will give the measurement to resize the case just below the chambers headspace in the firearm being reloaded for, giving a more accurate shot and saving brass by not causing it to be overworked.
Once the brass has been sized, set the brass in the gage and set the gage on a flat surface with the head side facing down. Now look across the top of the gage, this give the maximum and minimum for trim length.