Let me begin this installment with a reminder and a question. The components that make up a cartridge include the case, bullet, primer, and propellant. Which one is not readily inspected once your hand load is assembled?
Of course, the answer is the propellant charge. It’s completely obscured by the cartridge case.
I want to focus on how to pick the right propellant for one’s handloads. And please bear this in mind: Loading an incorrect propellant charge can be disastrous!
Common sense suggests that if you load the same safe charge weight of the same (correct) lot of propellant in each one of a batch of handloads, you’ll surely obtain more uniform ballistic performance. So how does one achieve such an obviously desirable condition?
Well, today’s handloaders have never had it so good. There are several methods to dispense and/or measure powder charges that are at the least acceptable and, depending on how deep your pockets are, quite precise.
The objective of selecting and dispensing propellant when handloading is to load a safe charge weight of the optimum powder. This activity is what engineers deem a “critical process” because there’s usually little or no margin for error. Therefore, you must carefully establish and rigidly follow a specific procedure to preclude the possibility of loading the wrong propellant charge.
You can verify the charge weight indirectly (with reasonable certainty) by weighing each cartridge and then subtracting the weight of a primed case and bullet. If the average value is pretty close to the desired charge weight and also comfortably below the specified maximum charge (and you still have the correct container on your bench), you can reasonably assume you’ve loaded the correct powder and charge weight. If not, you should carefully disassemble that batch and start over.
The Simple Answer
There are at least 150 different propellants available for hobbyist reloaders to choose from. How do you choose one that’s suitable for your specific load requirements?
The answer to that question is simple. Just consult several current editions of the major component suppliers’ load manuals and choose recipes to test for the specific cartridge and bullet type and weight you want to load. If Hodgdon’s H4350 delivered satisfactory performance in .30-06 and .243 Winchester handloads and you would like to also use it to load for your new 7mm Remington Magnum rifle, first check out the load manuals to verify it’s a safe choice and then give it a try.
However, if you’ve just acquired a Freedom Arms .454 Casull revolver, your perfectly suited rifle propellant is absolutely not going to work in even a magnum handgun cartridge. For this application, you’ll need to choose a powder like Hodgdon H110 or Alliant 2400 that exhibits a relatively much faster burn rate than H4350.
If you’re wondering what this burn rate means, well, as the term suggests, burn rate has to do with just how fast a propellant will ignite and be consumed when the cartridge is fired. Burn rate significantly affects how great the maximum pressure level will be and how quickly it occurs. Depending on several factors, a specific propellant or amount of propellant may or may not be compatible with the desired ballistic performance of your cartridge.
A cartridge case full of H110 will literally destroy a .30-06 rifle -and the shooter snuggled up to the action. On the other extreme, a .454 Casull cartridge filled with H4350 may not even ignite. Or it may experience a hangfire (delayed ignition). Or it could only partially ignite and leave the bullet stuck in the barrel.
Take a look at the propellants listed in your loading manuals for a specific cartridge and bullet weight and compare them to one or several burn rate charts. These charts typically list propellants from the fastest at the top to the slowest at the bottom. You will see that the recommended propellants will be, at least loosely, grouped together on the chart.
Now go back and look at the recommended charge weights of the propellants listed in the manuals. You’ll notice that the faster ones usually show lower maximum charges listed than the slower propellants. That’s because the physical configuration, chemical composition, and propellant coatings all affect how quickly they can be ignited and consumed.
You’ll also find other propellants listed in addition to the ones from a manual. They typically exhibit a similar burn rate and could possibly provide the desired performance. So, can you simply select a powder that’s close on the burn rate chart to those you’ve already tried and simply substitute the same charge weight?
That’s the pitfall of improperly using deductive reasoning in an apparently obvious manner. Just because another powder is listed near one you’ve tested or found a recipe for in your loading manual does not mean it is safe to substitute using the same data. If you look at another burn rate chart, you’ll probably note the relative positions of the two propellants you’re comparing may be separated farther apart or even reversed in relative positions!
The only safe scheme is to select load data from a reliable source and use it only if you can compare that data with a similar recipe found in another reliable source. Until you are an experienced handloader, it’s smart to stick with one or more of the various load manuals.
Next article I’ll discuss how to properly measure and verify propellant charges.