Three Critical Handloading Measurements

Handloading ammunition, especially for rifle shooters, is a precision-intensive endeavor. People who can't be bothered to deal with tolerances measured to one-thousandth of an inch or one-tenth of a grain should likely stick with shooting factory ammo. Fortunately, factory ammunition is getting better every year, and other than a per-shot cost increase, non-handloaders may not be giving up much in performance. For those who do reload their own ammo, precision shooting requires precision handloading. And precision handloading requires precision measuring. So, here are four critical measurements every handloader needs to know about, for both performance and safety.

Case Length

Repeated reloading causes brass cartridge cases to grow in length, and if they get too long, it can cause rifle malfunctions as well as serious safety issues. Modern designs have very little taper in the case body, and this helps reduce stretching. Older designs, like the .22-250, have a lot of taper and a valid reputation for growing too long from only a few firings. If a cartridge case is too long to fit in the rifle's chamber, it can cause a feeding malfunction when the bolt refuses to close. If the action does close on an overly long case, the constriction at the mouth of the case neck can cause pressures to skyrocket enough to damage the gun and the shooter.

Case length is always checked with a quality micrometer, and if it exceeds a set value, trimmed back using a bench-mounted tool designed for the job. Maximum case length is found in reloading manuals, where the industry-standard measurements set by SAAMI are listed. To be safe, case lengths should be set about 0.010-inch less than the maximum for that cartridge. So, for example, the 6.5 Creedmoor has a maximum case length of 1.920 inches. Therefore, a properly reloaded cartridge should have a case length of about 1.910 inches.

Headspace

Headspace is another cartridge case measurement, but it is measured differently depending on case design. However, for the bottleneck cartridges typically used in precision shooting, it's a measurement from the base of the case to a designated datum line on the case's sloped shoulder. Again, this measurement value is set by SAAMI. When a cartridge is fired, it swells to fill the rifle's chamber and must therefore be squeezed back down to something approaching its original dimensions to be reloaded. When this is done, leaving the headspace dimension too long will prevent the loaded cartridge from being chambered, while reducing headspace too much will shorten case life and eventually lead to case head separation.

Hitting that just right, "Goldilocks", dimension usually means reducing a resized case's headspace about 0.002-inch less than that of a case fired in the same chamber. Note that unlike cartridge case length, we don't use the SAAMI-designated measurement. This is because of chamber dimension tolerances involved in manufacturing, making it best to measure fired case headspace and work back a few thousandths of an inch from there. Most of the major handloading tool manufacturers offer devices for making this measurement, with the most practical being those which use the precision calipers already on every handloaders bench.

Cartridge Overall Length

A third critical measurement for handloaders is the overall length of a loaded cartridge. This is the total length of the loaded round, measured from the base of the cartridge case to the tip of the bullet. It's a measurement which ensures the round isn't too long to fit in a firearm's magazine or so long that the bullet contacts (jams into) the rifling lands of the barrel. The former situation turns a rifle into a single shot, while the latter can cause catastrophic overpressure.

Using the C.O.L. (cartridge overall length) listed in the bullet manufacturer's data for the specific bullet being used is normally a safe starting point. Shortening or lengthening the overall length can be done from that point once the handloader understands the ramifications of going in each direction. For example, reducing overall length while keeping everything else the same will increase pressure. Loading to a longer length will reduce pressures, at least until the bullet starts touching the rifling; then it can go up dramatically.

Again, a good caliper is needed to make an overall length measurement, as we are dealing with measurement increases or decreases of 0.001-inch. Accessory tools which complement the caliper and are made for measuring overall length are available from several sources.

A Common Caution

If you've been paying attention, you'll have noted that all three of these measurements use the base of the cartridge case as a common measuring point. This means the base of the cartridge needs to be free of any interference that could skew the measurement. For both case and headspace length, this means the expended primer should be removed prior to measuring. When measuring overall length, the primer will be in place, but check that it is seated below flush with the case head, as it always should be. Precision measurements aren't hard, especially with the proper tools. I find precision shooting is much more difficult.

About The Author

Al Voth calls himself a "student of the gun." Retired from a 35-year career in law enforcement, including nine years on an Emergency Response Team, he now works as an editor, freelance writer, and photographer, in addition to keeping active as a consultant in the field he most recently left behind—forensic firearm examination. He is a court-qualified expert in that forensic discipline, having worked in that capacity in three countries. These days, when he's not working, you'll likely find him hunting varmints and predators (the 4-legged variety)