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Measuring ABSOLUTE Headspace 

 

I have long advocated measuring fired cases in order to ascertain the headspace condition of a given rifle. In the case of the 8x57, I haven't found a case-measuring device.

Sometimes, the headspace may be suspect to the extent that it would be un-wise to attempt to fire the rifle. In these cases, no fired case could be obtained, much less measured.

So here is a device that will allow absolute measurement of the headspace without the need for firing.

Remember, GO, NOGO, and FIELD gauges don't allow absolute measurement, but only determine if the headspace dimension is greater or less than some limits.

Above is the stuff required to make the measurement, in this case I am using 8x57 components. At the top is a dial caliper. I got this one at either ENCO or Wholesale Tool, it's a 6 inch, stainless steel instrument and should cost $15. Beneath the caliper, at the left, a fired and RESIZED (or new) 8x57 case, a .45 cal bore brush, a 8x57 headspace gauge (doesn't matter GO, NOGO or FIELD), and a Wilson case length gauge.

Lets look at the Wilson gauge. It's a block of steel with a chamber cut to the dimensions of the 8x57 case. Wilson sells it to "measure" cases after resizing, and is designed to indicate if the case is to long or to short, measured from the base TO THE DATUM LINE.

To use this as intended, a resized case is "chambered", as seen above (I resized this Berdan case, but left the primer in). Now look closely at the "trench" across the top of the gauge. A properly sized case will not extend above the gauge, nor will it fall below the floor of the "trench".

This case is a tad to long, as it extends above the gauge.

This case falls below the floor of the trench, and is to short.

A properly sized case will fall somewhere in between.

While this is a very necessary tool for a reloader (you can't really do quality hand loading without it or something like it) I will be using it in another way.

OK, lets build a gauging device! Start by cutting the head off of a fired (or new) case. I am using a Berdan case, but better (easier) results can be had with a Boxer case.

The cut case should look like this. Shorten the case mouth by about a 1/16 inch and smooth the cut edges, inside and out.

Then drill through the head with a 1/8-inch or #29 drill. If using a Boxer case, you already have a nicely centered pilot hole.

If using a Berdan case, carefully center punch the inside of the case, a transfer punch is useful here, then drill.

Now tap the hole you just drilled using a 8x32 tap, and screw in the 45 cal bore brush until tight.

Just to make sure, put some clay on the end of the case, and fill the head with AcraGlas.

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