After reading this posting I would like to add a few facts, the average American new unfired cartridge case is approximately .002 (two thousandths) shorter than minimum head space for a given caliber.

A fired case that has been full length resized “should” be under minimum head space BUT this depends on the accuracy of your shell holder dimensions, the accuracy of your resizing die and “how” the die is set up in the shell holder.

How do I know this, I have been reloading for over 40 years and I have gauges to check the length or cartridge head space.

[img width=600 height=450]http://i122.photobucket.com/albums/o254/bigedp51/IMGP5130-1.jpg[/img]



Knowing that a new unfired case is approximately .002 shorter than minimum head space and “if” you have a set of vernier calipers you could use an unfired case to setup your barrel for proper head space.

Step 1. Take the case you plan to use and measure the case length with your vernier calipers and write the measurement down.

[img width=600 height=450]http://i122.photobucket.com/albums/o254/bigedp51/IMGP0710.jpg[/img]

Step 2. Take a fired spent primer and partially start the primer in the primer pocket.

[img width=564 height=450]http://i122.photobucket.com/albums/o254/bigedp51/IMGP0704.jpg[/img]

[img width=600 height=450]http://i122.photobucket.com/albums/o254/bigedp51/IMGP0706.jpg[/img]

Chamber the case, eject and re-measure the case length, you want this measurement to be approximately .004 to .005 larger than your first case measument. What you are striving for is a head gap clearance or air gap between .002 and .003 thousandths at the rear of the case and the bolt face.

Below, an example of excessive “head gap clearance” or the “air gap between the rear of the case and the bolt face on a .303 British Enfield.

[img width=600 height=272]http://i122.photobucket.com/albums/o254/bigedp51/9-2.jpg[/img]

I reload and prefer tight head space because it helps prevent stretching and thinning in the case web area of the case and helps promotes accuracy, BUT sometimes the word head space means nothing.