Moving Ahead With HEAD SPACING

Guns Magazine, April, 2001 by Charles E. Petty

Now there is an easier way to determine proper head spacing for partial resizing than the old trial-and-error method. Redding's Instant Indicator allows you to measure the true headspace of your rifle easily with accuracy to the nearest thousandth of an inch.

At first glance it looks like a standard loading die with a dial indicator sticking out of the top. Actually that's not far off, but inside the die body is a precisely shaped "shoulder contactor," which is spring loaded via a spacer so the dial indicator gets a precise reading. To set up the Instant Indicator, Redding provides a beautifully machined brass "setup gauge," which is made to the exact specification for the minimum chamber established by SAAMI.

With that done and the dial indicator adjusted to zero, replacing the setup gauge with a case fired in your rifle will show how your rifle compares to the minimum. SAAMI has a 0.010" tolerance from minimum to maximum, so the first thing the Instant Indicator displays is whether your rifle is up to snuff.

For example, if your case reads 0.005" larger than the gauge, it's right in the middle of the range. When you reload it, you want to more the shoulder as little as possible -- just two- or three-thousandths for most purposes -- so you simply adjust the sizing die so that the Instant Indicator reads 0.002" to 0.003". This is just the right amount of shoulder bump for most cases. Lock the sizing die down and you can load over and over until the brass needs trimming or something else changes.

Redding warns that it's best to make the setup adjustments with a case that has been fired at least twice. If you start with factory ammo, the fired case may not completely fire form to your chamber with just one shot.

We discovered this with a .223 bolt action firing factory ammo. All of the once-fired cases showed between -0.002" and -0.003". The same cases were sized just enough to hold a bullet and fired again. This time the reading was 0.003".

The combination of a small-diameter case and relatively moderate pressure simply did not fully form the case against the chamber. The next time it did. Now this is not an everytime thing, but it can happen, and since you're not suppposed to have negative headspace, it can be a bit puzzling.

The Instant Indicator can also be used to properly measure bullet-seating depth. Since the overall length of bullets can vary, measuring at the tip can lead to some real variations between rounds. Better to measure from the datum point on the bullet ogive.

You can also measure the uniformity of bullets -- also from the ogive by a slight adaptation of the Instant Indicator. Ditto for case length. Simply set up and zero the indicator on a case of the length you wish to maintain and easily see when it's time to trim.