POWDER GRAIN SHAPES — What You Need to Know

The shape of powder grains has a profound effect on the performance of the powder charge, as it concerns both pressure and velocity. There are multiple powder shapes including flake, ball, and extruded or “stick” (both solid and perforated).

All Vihtavuori reloading powders are of the cylindrical, single-perforated extruded stick type. The differences in burning rate between the powders depend on the size of the grain, the wall thickness of the cylinder, the surface coating and the composition. Cylindrical extruded powders can also have multi-perforated grains. The most common types are the 7- and 19-perforated varieties. A multi-perforated powder grain is naturally of a much larger size than one with a single perforation, and is typically used for large caliber ammunition.

Other types of powder grain shapes include sphere or ball, and flake. The ball grains are typically used in automatic firearms but also in rifles and handguns. The ball grain is less costly to produce, as it is not pressed into shape like cylindrical grains. Flake shaped grains are typically used in shotgun loadings.

Web thickness in gunpowder terminology means the minimum distance that the combustion zones can travel within the powder grain without encountering each other. In spherical powders, this distance is the diameter of the “ball”; in flake powder it is the thickness of the flake; and in multi-perforated extruded powders it is the minimum distance (i.e. wall thickness) between the perforations.

The burning rate of powder composed of grains without any perforations or surface treatment is related to the surface area of the grain available for burning at any given pressure level. The change in the surface area that is burning during combustion is described by a so-called form function. If the surface area increases, the form function does likewise and its behavior is termed progressive. If the form function decreases, its behavior is said to be degressive. If the flame area remains constant throughout the combustion process, we describe it as “neutral” behavior.

The cylindrical, perforated powders are progressive; the burning rate increases as the surface area increases, and the pressure builds up slower, increasing until it reaches its peak and then collapses. Flake and ball grains are degressive; the total powder surface area and pressure are at their peak at ignition, decreasing as the combustion progresses.

So how does the shape affect pressure and muzzle velocity? In general, it can be said that powder that burns progressively achieves a desired muzzle velocity at lower maximum pressure than a powder that burns neutrally, not to mention a degressive powder. As grain size increases, the maximum pressure moves towards the muzzle, also increasing muzzle blast. Muzzle velocity and pressure can be adjusted by means of the amount of powder or loading density, i.e. the relationship between the powder mass and the volume available to it. As the loading density increases, maximum pressure grows.

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This article originally appeared on the Vihtavuori Website.

Popular Powders In Stock at Brownells at Reasonable Prices

We all know that reloading powders have been hard to find. And when you do find an appropriate powder, some vendors are asking crazy high prices. Well we’re pleased to report that Brownells has a number of popular powders IN STOCK today (11/20/2021), and the prices are quite fair, starting at $24.99 per pound for Ramshot Competition. Grab some excellent Hodgdon H380 for $33.99 per pound, or IMR 4198 for $38.99 per pound. CLICK HERE to see all available in-stock powders at Brownells today.

Save Money with Brownells Discount Codes

While you’re shopping at Brownells, don’t forget to use one of the current Discount Codes to save money. There are many current codes that can save you up to 10% on your purchase. And with special Pre-Black Friday Code RTC you get $30 off $300 PLUS FREE Shipping and handling through November 23rd at midnight. Fill in the applicable Code during checkout.

Current Brownells Discount Codes:

Code FR6: $85 off $875
Expiration date November 30, 2021

Code Q63: Free Shipping/Handling over $99
Expiration Date Unknown

We all know reloading powder is in VERY short supply these days. And the most popular propellants, such as Varget, H4350, and Reloder 16, are almost impossible to find at reasonable prices. Thankfully, there is a new solution in the works — smaller containers. This should give handloaders a whole new way to source those precious powders needed for a day at the range. And even if the volume is limited, something is ALWAYS better than nothing, right?

The big (and small) news for reloaders is that the major powder suppliers plan to start shipping powders in more compact, easy-to-ship containers. Instead of buying a pound of powder, you will be able to purchase an efficient, handy 1000 grain container. These are light weight (just 1/7th of a pound) so they are convenient to transport and carry. And you’ll never have the problem of over supply. A 1000-grain container with load approximately 33 6mm BR rounds — that should be plenty for a day at the range. We’re blessed to have this new compact powder option thanks to the U.S. Department of Transportation (DOT).

The U.S. Department of Transportation (DOT) recently approved new smaller containers for shipment of smokeless powder. The new containers are designed to hold 1000 grains, exactly one-seventh of a pound. That works out to 2.29 ounces of powder — quite a bit less than you are getting currently with one-pound (16 oz.) containers.

Here how it works out:
7000 grains = 1 pound = 16 ounces
1000 grains = 0.143 pounds = 2.29 ounces

Many products — from cereal boxes to Snickers bars — have been down-sized in recent years. Now downsizing has come to the powder marketplace. The strategy behind the smaller containers is simple. In a market where demand vastly outstrips available supply, the smaller containers allow powder-makers to generate more revenue with a given amount of powder inventory. Will consumers accept the smaller powder containers? Probably so — 1000 grains is enough to load 20-22 rounds of .308 Winchester. In the current marketplace (with many powders virtually impossible to find), most consumers would probably prefer to get 2.3 ounces of their favorite powder, rather than nothing at all. (NOTE: The major powder suppliers will continue to offer popular powders in 1-lb, and 8-lb containers. The new 1000-grain containers will be phased-in over time, as an alternative to the larger containers).

Why the small bottles? One industry spokesman (who asked not to be named) explained: “We’ve had a severe shortage of smokeless powder for nearly two years. The powder production plants are running at full capacity, but there’s only so much finished product to go around. By moving to smaller containers, we can ensure that our customers at least get some powder, even if it’s not as much as they want.”

Why are the new containers 2.3 ounces rather than 8 ounces (half a pound) or 4 ounces (one-quarter pound)? One of the engineers who helped develop the new DOT-approved container explained: “We looked at various sizes. We knew we had to reduce the volume significantly to achieve our unit quantity sales goals. Some of our marketing guys liked the four-ounce option — the ‘Quarter-Pounder’. That had a nice ring to it, but ultimately we decided on the 1000 grain capacity. To the average consumer, one thousand grains sounds like a large amount of powder, even if it’s really only 2.3 ounces. This size also made it much easier to bundle the powder in six-packs. We think the six-packs will be a big hit. You get nearly a pound of powder, but you can mix and match with a variety of different propellants.”

Less Bang for Your Buck?
We’re told the new 2.3-ounce powder bottles will retail for around $11.99, i.e. about $5.21 per ounce. At that price, it may seem like you’re getting less bang for your buck … but hey, something is better than nothing, right?

Currently, when you can find them, quality reloading powders are going for $45-$60 per pound (in 1-lb containers). At $45 per pound, you’re paying $2.81 per ounce. That means that the new mini-containers will be roughly twice as expensive as current one-pounders ($5.21 per ounce vs. $2.81 per ounce).

Along with the 2.3-ounce containers, the DOT has approved “six-pack” consolidated delivery units that will hold six, 1000-grain containers. Some manufacturers plan to offer “variety packs” with a selection of various powders in the 1000-grain bottles. Wouldn’t it be cool to have a six-pack with H322, H4895, Varget, H4350, H4831sc, and Retumbo?