Both of the topics I’m covering here were prompted by an ever-building series of reader emails and phone calls concerning these subjects. Since both of them can—and almost always do—lead to dangerous pressure levels, I felt it important to get my explanations, responses and cautions on record in the interest of safety and reliable performance.
Adapting Long-Shell Recipes into Shorter Shells
Let’s start with the misguided practice about which I receive the most correspondence: the decision to take a proven and tested loading recipe for a longer shell length and alter it to fit into a shorter shell. The reasons I’m often given from those who decide to do this are:
- “My gun is chambered for 2½" shells, and I can’t find any 2½" loading recipes except those using powders and/or primers currently unavailable. So I decided to adapt a 2¾" recipe that has components I can still buy to fit into the shorter 2½" shell length.”
- “Adapting a longer shell recipe for a shorter shell length allows me to avoid having to mess with inserting sub-gauge card wads to take up space.”
- “The Internet posters keep saying that if a longer recipe will fit into a shorter shell, ‘No problem, no worries.’”
Let’s look at these in order. First, yes, I know the current powder, primer and (certain) wad shortages are frustrating many shotshell handloaders. But you can’t just throw caution to the wind for the sake of convenience. An ironclad ballistic fact is this: Any time a safe recipe for a long shell is altered to fit into a shorter shell, the resulting chamber pressure will definitely rise. How much? Typically, a pressure rise of 1,500 to 2,000 psi is common in 12 gauge. And the smaller the gauge of the load recipe that is being altered, the greater the rise will be to the resulting pressure.
It’s all a matter of internal volume. The shorter the length and the smaller the gauge of a given shotshell hull, the less internal volume it offers. The smaller the internal volume, the greater the pressure rises for any given recipe, as pressure is a function expressed as pounds per square inches of space. Simply put: Reduce the square inches, or volume, inside the shell, and the pounds increase. This can be controlled only by loading a slower-burning propellant and/or cooler primer. But in the case of a handloader simply altering a larger-volume (longer-shell-length) load to fit into a smaller-volume (shorter-shell-length) hull without knowing enough or doing any pressure testing to identify the correct slower-burning powder or cooler primer to keep the pressure down, the result will always be a significant rise in pressure that frequently exceeds the maximum limit established by SAAMI or CIP.
Second, as mentioned, the most common method detailed to me for making long-shell recipes fit into shorter shells is that readers either leave out sub-gauge filler wads or load a one-piece wad with shorter cushioning posts until everything fits. What’s lacking in understanding here is that collapsing plastic cushioning posts or compressing fiber, felt or cork wads is vital to the successful ballistics of a shotshell load. Collapsing or compressing these wads increases the internal volume of the shell and thus keeps pressure down. And in the case of soft shot types like lead or bismuth, this also is vital to protecting the pellets from deformation.
As to the third reason, I repeat my caution ad infinitum to believe almost nothing you read on the Internet about loading shotshells. The posters almost universally are simply shotgun enthusiasts, have no access to pressure- and velocity-testing equipment, and have no training or work experience in the shotshell-ballistics-and-manufacturing field.
Substituting Different Shot Types
All loading data for shotshells clearly stipulates a given shot type for the recipe that follows. The shot types are currently lead or steel or bismuth or tungsten composite. I’ve repeated the word “or” here to emphasize that loading data is always separated and isolated by shot type. This simply and unwaveringly means that if you want to load lead, you use lead-shot loading data; to load bismuth, you use bismuth-shot loading data; to load tungsten composite, you use the specific tungsten-composite shot type stipulated. (And there are several tungsten-composite shot types—all of which vary by hardness and density.)
I was first surprised and now have become alarmed by the number of shotgunners contacting me about loading a specific tungsten-composite type using lead-shot loading data or one tungsten-composite type using loading data for another tungsten-composite type because “tungsten is just tungsten.” Now, pressure is not just pressure, and all tungsten-composite pellets are not the same just because they all contain tungsten.
The reality is that each shot type, because it contains a specific metal mixture, creates its own set of unique ballistic results. Each shot type has its own density and hardness levels. These interact to resist the shot-crushing and -deforming forces inside the shell when it fires and thus also play a role in reducing or increasing the resulting pressure of a given recipe. The higher the density and/or the harder the shot type, the more resistant it is to deforming. And pellet deformation absorbs energy, which in turn reduces pressure. So substituting a harder and/or denser shot type into a recipe designed for loading a softer and/or less-dense pellet type will always raise pressure. How much? Again my testing has shown a typical 1,500- to 2,000-psi pressure rise in 12 gauge—and even greater, the smaller the gauge in which the substitution is taking place. So one is playing with fire by substituting so-called tungsten shot into lead-shot recipes or higher-density tungsten-composite shot into lower-density tungsten-composite-shot recipes.
The wise shotgunner will heed all of these ballistic realities and not mess with creating his or her own shotshell loads based on personal theories about why altering a published recipe would be safe. Altering a shotshell recipe not based on pressure and velocity ballistic-lab testing almost always results in unsafe loads or loads approaching unsafe. This won’t wreck your gun right away. But since the effect is cumulative, in time damage like broken metal parts, cracked wood, split or ruptured barrels, and even injury to your hands and face can result.
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