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Shotshell Pressure: How to Avoid Trouble

Categories:: Gun Articles • Reloading
Rick Sapp | Oct 05, 2010 | Comments 0

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Cold weather can be a problem for a slow burning powder in a hunting load and, depending on the temperature, will affect your hotter-burning target loads as well.

FIRE IN THE HOLE!

So, what happens when you pull the trigger? The powder is ignited. It begins combining furiously with its own oxygen to create an ever-expanding column of ultra-hot gas, but at a constant pressure (for maximum pellet velocity), and that column takes up an increasing volume of space. This is what pushes the shot out toward the flying pigeon. When the shotcup leaves the barrel, air resistance causes it to fall away within about 10 yards, and the speeding shot rushes on toward its intended target, although its velocity begins to diminish immediately upon exiting the barrel.

The column of hot gas is engineered to balance the burning powder with the expanding volume. Hence, powders are grouped by “burn rates.” If all of the powder burns before the shot passes the forcing cone, the shot may begin slowing down inside the barrel and that, obviously, is not going to give you the perfect solution to any shooting problem. Here are the generally accepted guidelines, but remember that engineers develop loads for practically every possible combination and circumstance, so these are only “rules of thumb”:

- Lightweight loads with moderate velocity, typically target and small game loads, fall into a faster burning powder category. (Example: Introduced in 1992, Hodgdon’s Clays “produces soft, smooth recoil, ultra clean burning, mild muzzle report and excellent patterns.”)

- Heavier hunting loads, which typically have greater velocities, predominantly use slow-burning powders. (Example: Introduced 85 years ago, Alliant’s Herco is a “proven powder for heavy shotshell loads.”)

Load for your 12-gauge with Hodgdon’s Clays and Titewad, especially for target and light field reloads. Clays and Titewad are also rated for competition pistol reloads in the 45 ACP and 38 Special. Clays, Hodgdon says, produces “soft, smooth recoil” and burns “ultra-clean” with a mild muzzle report and excellent patterns. Titewad is a “flattened spherical” powder with low charge weight, “mild muzzle report, minimum recoil and reduced residue for optimum ballistic performance.”

Load your 12-gauge with Hodgdon’s Clays and Titewad, especially for target and light field reloads. Clays and Titewad are also rated for competition pistol reloads in the 45 ACP and 38 Special.

Powder burn rates are important. Many hunters endure the foulest, coldest weather to hunt deer or waterfowl, and our Canadian cousins revel in organizing sporting clays events when orange birds show up remarkably well against mounds of snow and ice. With an already slow-burning powder, low temperatures can cause a problem on a frigid morning in a Maryland duck blind.

We know that cold retards ignition and causes powder to burn slower. To optimize your shotgun’s performance in these conditions, you need specially constructed loads perhaps upgrading to a medium burn rate powder. You may also want to consider using heavier loads and new hulls for stronger crimps. Hot primers are more likely to cause good powder ignition in cold weather because they were developed for just such a situation.

This is precisely why handloading is such a virtuous pastime for shotgunners. It allows us to craft loads for conditions, and to laugh at our over-the-counter buying cousins. Different recipes will give you different results and you can load differently for hot days than for cold days. (To be honest, even experienced shotgunners usually cannot perceive any difference in their load performance as temperature changes, but they are aware that there is a difference.)

Although they do for the most part list velocities for over-the-counter shells, ammunition companies do not publish pressures for their commercial loads in either their catalogs or on their Internet sites. Ammo manufacturers are often stingy about revealing the amount of powder in loads as well, preferring simply to list that number (that number being the relatively archaic “drams equivalent”) as “max.” Of course, there may be a good reason for this.

This article is an excerpt from Reloading for Shotgunners, 5th Edition. Click here to learn more or get your copy.

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