In this graphic portrayal of average and dynamic V/C ratio, the plots diverge when chamber pressure exceeds safe levels. (Courtesy of Johan Loubser)

First, how many reloading articles have you read that contain the standard mantra "start with the minimum charge listed and work up as pressure signs indicate it is safe?" So what exactly are these "pressure signs?" Sticky bolt lift? Leaking primer pocket? Flattened primers? Swollen case heads?

Actually, when any of these indications are evident, you've surely already exceeded safe pressures--hopefully without having caused permanent damage to you or your rifle.

There is a better way to work up a safe load. While most of us can't measure pressure, we can readily measure bullet velocity. The only special equipment you need--an accurate chronograph--is well within the means of most handloaders.

I first read about the velocity-to-charge (V/C) ratio several years ago in a loading manual published by the Somchem Ballistic Laboratory in South Africa. Simply stated, it's the bullet velocity divided by the propellant charge weight. The author was Johan Loubser, who is now the ballistician at Western Powder in Montana.

I met Loubser nearly 10 years ago in the Accurate Powder booth at the SHOT Show. The South African native struggled to effectively communicate with this ol' Southern boy. Eventually, he was successful in teaching me a few things about reloading. Fortunately, when Western Powder acquired Accurate a few years ago, my friend was part of the package.

Before immigrating to the U.S., Loubser was the ballistic specialist at Somchem's lab near Cape Town. The company's loading booklet included Loubser's insights on various ballistic performance parameters in addition to the usual load recipes. Promoting the quantitative premise of "if you don't measure it, you can't manage it," he offered a relatively simple method to help shooters assess handload performance.

First, assemble five rounds using the minimum powder charge suggested by your reloading manual. Next, fire them to determine the average velocity. Then calculate the handload's V/C ratio and compare it to the V/C values derived from recommended load data in your loading manual. Of course, you must compare apples to apples--same powder type, equal barrel length, same weight bullet, etc.

If the calculated V/C for your handload is higher as compared to the ratio derived from the load manual data, then your ammo/firearm system is generating higher pressures. You may hit the maximum load for your rifle before reaching the maximum charge weight indicated by the manual. Conversely, if the V/C ratio is lower, your system is operating at relatively lower pressures. In order to achieve maximum velocity, you may have to exceed the recommended maximum powder charge.

Loubser stated the average V/Cs for charge weights within the recommended start and max range should be almost constant. As you increase the charge further, both pressure and velocity change from a relatively linear to an exponential progression. He refers to this as the dynamic V/C range (see the graph on page 28). When the dynamic V/C exceeds 1.5 times the average V/C, pressures have become unstable, and you should back off the powder charge.

I reviewed an earlier column on developing a safe .30-06 handload using Alliant Reloder 19 and a 180-grain Sierra GameKing bullet. I've modified the chart to add the average and dynamic V/C values for each test load and retained the velocity and pressure data for reference. As you can see in the accompanying chart, the average V/C numbers are stable as the dynamic values bounce around some.