Cartridge headspace measurements

[dmazur]

I thought I'd try Hornady's "headspace bushings". These are available as a complete kit, or separately. If you already have the Hornady bullet comparator, you have the caliper adapter. Then all you need is a bushing or two, depending on how many cartridges you reload.

It seemed like a relatively low-cost experiment, so I ordered a bushing for .30-06 and another for .243.

They are relatively easy to use, and if all you're trying to do is measure fired cases and adjust a resizing die for a desired headspace, they work fine. These are "relative" measurements.

However, I decided I was going to record actual case length (to datum) and that's where the fun started...

I used chamber headspace gauges for a known starting point (one in each caliber.) These measure 0.000" from the top step on my Wilson case gauges for further verification.

For one bushing, I had to subtract 1.995", and for the other bushing I had to subtract 1.998" from the length shown on the dial caliper, in order to get the marked length of the chamber gauge.

This is just so close to 2.000" I can't help but wonder if that was Hornady's intent.

And then there's this -

http://www.thehighroad.org/showthread.php?t=504759&highlight=hornady+headspace

which is making one yourself.

 

[woods]

Just reset it to an even 2" every time


and reset your caliper to 1" with the comparators


like you say it is all relative

Be sure and put the tightening knurl nut on the bottom on the other side from the caliper face. It is offset.

 

[dmazur]

Thanks.

That's so simple I just couldn't see it.