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  • Writer's pictureJason Stanley

Reloading: Measuring Equipment

Updated: Mar 20

This is the first installment of a multipart Blog all about rifle reloading. These blogs will be organized based on steps in the reloading process. Organizing it this way will make it easier to find answers to questions you may have.

Here are my top two rules while reloading:

# 1 Rule = Safety

# 2 Rule = Everything you do should be repeatable

Measuring Tools

Accurate measurements are vital if the reloading process is to be repeatable. Accurate data requires the correct tools. Here are some measuring tools that you will find on my reloading bench.


Construction workers have tape measures. Reloaders have calipers. Just like a builder uses a tape measure constantly during their work day, a reloader will constantly use their calipers. Very seldom do I work in the reloading room and not use a caliper.


When I need a correct fourth decimal spot, I use the micrometer. For example, when finding the Over Bullet Measurement (OBM) requires a micrometer. This measurement is used when finding the neck clearance and neck tension. Calipers simply are not accurate enough for this important measurement.

Ball Micrometer

I use a ball micrometer when measuring the thickness of the case neck. This measurement, along with some math, will give me a theoretical idea of my over bullet measurement used when neck turning brass. I then confirm with a seated bullet using the micrometer.

Both my micrometer and ball micrometer are attached to a micrometer stand. This makes measuring objects much easier.

Note: If I had to start over, I would purchase calipers that have a ratcheting thimble. Both my micrometer and ball micrometer have this feature and it makes obtaining accurate and repeatable measurements easier.

Headspace/Chamber gauge

A Chamber gauge will be used in conjunction with the caliper. The chamber gauge measures how much the case shoulder is being bumped back when the case is resized.

For custom barrels, the gunsmith will make me a chamber gauge by partially running the chamber reamer into a scrap piece of barrel. On factory barrels I use Hornady’s Lock-n-Load Headspace Gauge. Both tools are used in the same way.

Bullet Comparator

I use Hornady’s Lock-n-Load Bullet Comparator when finding my B.O.L. (Base to Ogive Length) This is the measurement I use when making sure the bullet seating depth is correct.

B.O.L. is consistently more accurate than the C.O.L. (Cartridge Overall Length). Actually, the only time I use C.O.L. is in confirming my loaded rounds fit in the magazine.

Precision on the target starts with precision while reloading. Learn how to use these tools and you will be on your way to shooting smaller groups. Until next time, enjoy the process.

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