Head space comparator gage

[JScott]

I am getting ready for the upcoming Alabama turkey season.  This year I want to use my Thompson Contender pistol in .218 Bee.  One of the details for handloading ammunition for it is getting the correct head space so that the cartridges fire when they are supposed to and aren't over worked by being "stretched" during firing.  Keeping the head space at a minimum value makes this all easier.

To measure the head space I could have purchased a gage online but the design is very straightforward so I made my own.  The basic idea is a cylindrical gage that measures offset from a datum.  In this case the datum is the face of the barrel and the offset is the cartridge protrusion from the barrel.  The head space in my pistol is 0.010" which I measured with my feeler gage set.  I will load the ammunition so that the cartridges protrude 0.008-0.009" from the chamber.

Here is my version which should work for my simple application.  I used a piece of high strength bolt and did all the operations on the mill.  The set screw is 1/4-28 with a piece of lead shot at the bottom to protect the shank of the dial indicator.  The indicator is offset 0.139" from the center of the gage so that it rests on the head/rim of the cartridge case and not on the primer.  I will be using it this weekend so everybody keep your fingers crossed!