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).

So how does powder grain 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.

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.

Learn More with FREE Vihtavuori Reloading APP »

This article originally appeared on the Vihtavuori Website.

Widener’s Reloading & Shooting Supply has published a helpful introduction to reloading powders. Widener’s online Guide to Smokeless Powders shows the various types of powders, and explains how the differences in powder kernel/flake size and shape, and burn rate affect performance. We recommend you visit Widener’s website and read the Powder Guide in full.

Take a close look at these illustrations which show the key differences between the four main powder types: extruded (stick) powder, ball (spherical) powder, flattened ball powder, and flake powder.

Burn Rate Basics

Widener’s Guide to Smokeless Powders also has a useful discussion of Burn Rate (a confusing topic for many hand-loaders). Wideners explains: “While a gun powder explosion in the cartridge seems instantaneous, if you slow it down you will actually find that each powder has a different ‘burn rate’, or speed at which it ignites.” This video shows powders with two very different burn rates. Watch closely.

Different burn rates suit different cartridge types notes Widener’s: “In general a fast-burning powder is used for light bullets and low-speed pistols and shotguns. Medium-rate powders are used for magnum pistols, while high-velocity, large bore rifle cartridges will need slow powders[.]

It should be noted that burn rate does not have a standardized unit of measurement. In fact, burn rate is really only discussed in comparison to other powders; there is no universal yardstick. Specifics will change by cartridge and bullet types[.]”

Story by Boyd Allen
While many top competitive shooters trickle their stick powder charges to a kernel or two, that would be impractical when loading charges for giant naval guns. You may be surprised, but the shells fired by the U.S. Navy’s massive 14″ and 16″ naval guns were also propelled by stick-type extruded powders. You couldn’t trickle these ‘kernels’ though — a single stick or ‘grain’ can be over 2″ long.

The U.S.S. Iowa fires her massive 16″ main battery. The U.S. Navy’s Iowa-class battleships carried nine huge 16-inch Mark 7 cannons in three turrets. The big naval guns were 50 calibers long, i.e. 50 times bore diameter, making the barrels 66.7 feet long from chamber to muzzle.

In connection with a Benchrest Central discussion that drifted to the subject of powders used in large naval guns, I heard from Joe McNeil, whose father was involved in manufacturing those very propellants as a DuPont employee. Joe writes:

“My Dad worked for the DuPont company for over 40 years. Every time the nation went to war he was assigned to the gun powder plants which DuPont ran for the government for $1.00 per year! His last assignment was at the Indiana Ordnance Plant in Jefferson, Indiana from 1952 through 1958. He had a display case made of all of the different powders made at the plant and left it to me. That’s why I have a grain of 16″ gun powder. He took me out to the Jefferson proving grounds once when they tested the powder in a 16″ gun. We watched from a half-mile away but it left a lasting impression when they fired that gun. They actually had a set of rings they fired through to test the performance of the powder and shell. This was a truly fond memory of my Dad and his work.”

Here are some pictures of the gun powder “grains” made during the Korean War at the Indiana Ordnance Works where Joe McNeil’s father worked.

Above is the display case with the different powders manufactured at the DuPont plant. They include: 37 MM/AA, 75MM Pack Howitzer, 50 Cal. 5010, 20 MM 4831, 30 Cal. 4895, 76 MM, 3″, 5″, 90 MM, 4.7″, 240MM, 8″, 280 MM, 175 MM, 155 MM Howitzer, 155 MM Gun M.P., 8″ Gun M.P., 12″, 14, 16″. There are different-sized ‘grains’ for specific rounds.

16-inch/50-caliber gun projectile plus six propellant bags. Display mockup aboard U.S.S. Iowa (BB-61) in San Pedro, CA. Photo by James Madison per Creative Commons CC-BY-SA-4.0 license.

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).

So how does powder grain 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.

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.

Learn More with FREE Vihtavuori Reloading APP »

This article originally appeared on the Vihtavuori Website.

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).

So how does powder grain 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.

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.

Learn More with FREE Vihtavuori Reloading APP »

This article originally appeared on the Vihtavuori Website.

Story by Boyd Allen
While many top competitive shooters trickle their stick powder charges to a kernel or two, that would be impractical when loading charges for giant naval guns. You may be surprised, but the shells fired by the U.S. Navy’s massive 14″ and 16″ naval guns were also propelled by stick-type extruded powders. You couldn’t trickle these ‘kernels’ though — a single stick or ‘grain’ can be over 2″ long.

The U.S.S. Iowa fires her massive 16″ main battery. The U.S. Navy’s Iowa-class battleships carried nine huge 16-inch Mark 7 cannons in three turrets. The big naval guns were 50 calibers long, i.e. 50 times bore diameter, making the barrels 66.7 feet long from chamber to muzzle.

In connection with a Benchrest Central discussion that drifted to the subject of powders used in large naval guns, I heard from Joe McNeil, whose father was involved in manufacturing those very propellants as a DuPont employee. Joe writes:

“My Dad worked for the DuPont company for over 40 years. Every time the nation went to war he was assigned to the gun powder plants which DuPont ran for the government for $1.00 per year! His last assignment was at the Indiana Ordnance Plant in Jefferson, Indiana from 1952 through 1958. He had a display case made of all of the different powders made at the plant and left it to me. That’s why I have a grain of 16″ gun powder. He took me out to the Jefferson proving grounds once when they tested the powder in a 16″ gun. We watched from a half-mile away but it left a lasting impression when they fired that gun. They actually had a set of rings they fired through to test the performance of the powder and shell. This was a truly fond memory of my Dad and his work.”

Here are some pictures of the gun powder “grains” made during the Korean War at the Indiana Ordnance Works where Joe McNeil’s father worked.

Above is the display case with the different powders manufactured at the DuPont plant. They include: 37 MM/AA, 75MM Pack Howitzer, 50 Cal. 5010, 20 MM 4831, 30 Cal. 4895, 76 MM, 3″, 5″, 90 MM, 4.7″, 240MM, 8″, 280 MM, 175 MM, 155 MM Howitzer, 155 MM Gun M.P., 8″ Gun M.P., 12″, 14, 16″. There are different-sized ‘grains’ for specific rounds.

16-inch/50-caliber gun projectile plus six propellant bags. Display mockup aboard U.S.S. Iowa (BB-61) in San Pedro, CA. Photo by James Madison per Creative Commons CC-BY-SA-4.0 license.

Widener’s Reloading & Shooting Supply recently published a helpful introduction to reloading powders. Widener’s online Guide to Smokeless Powders shows the various types of powders, and explains how the differences in powder kernel/flake size and shape, and burn rate affect performance. We recommend you visit Widener’s website and read the Powder Guide in full.

Take a close look at these illustrations which show the key differences between the four main powder types: extruded (stick) powder, ball (spherical) powder, flattened ball powder, and flake powder.

Burn Rate Basics

Widener’s Guide to Smokeless Powders also has a useful discussion of Burn Rate (a confusing topic for many hand-loaders). Wideners explains: “While a gun powder explosion in the cartridge seems instantaneous, if you slow it down you will actually find that each powder has a different ‘burn rate’, or speed at which it ignites.” This video shows powders with two very different burn rates. Watch closely.

Different burn rates suit different cartridge types notes Widener’s: “In general a fast-burning powder is used for light bullets and low-speed pistols and shotguns. Medium-rate powders are used for magnum pistols, while high-velocity, large bore rifle cartridges will need slow powders[.]

It should be noted that burn rate does not have a standardized unit of measurement. In fact, burn rate is really only discussed in comparison to other powders; there is no universal yardstick. Specifics will change by cartridge and bullet types[.]”

Story by Boyd Allen
While many top competitive shooters trickle their stick powder charges to a kernel or two, that would be impractical when loading charges for giant naval guns. You may be surprised, but the shells fired by the U.S. Navy’s massive 14″ and 16″ naval guns were also propelled by stick-type extruded powders. You couldn’t trickle these ‘kernels’ though — a single stick or ‘grain’ can be over 2″ long.

The U.S.S. Iowa fires her massive 16″ main battery. The U.S. Navy’s Iowa-class battleships carried nine huge 16-inch Mark 7 cannons in three turrets. The big naval guns were 50 calibers long, i.e. 50 times bore diameter, making the barrels 66.7 feet long from chamber to muzzle.

In connection with a Benchrest Central discussion that drifted to the subject of powders used in large naval guns, I heard from Joe McNeil, whose father was involved in manufacturing those very propellants as a DuPont employee. Joe writes:

“My Dad worked for the DuPont company for over 40 years. Every time the nation went to war he was assigned to the gun powder plants which DuPont ran for the government for $1.00 per year! His last assignment was at the Indiana Ordnance Plant in Jefferson, Indiana from 1952 through 1958. He had a display case made of all of the different powders made at the plant and left it to me. That’s why I have a grain of 16″ gun powder. He took me out to the Jefferson proving grounds once when they tested the powder in a 16″ gun. We watched from a half-mile away but it left a lasting impression when they fired that gun. They actually had a set of rings they fired through to test the performance of the powder and shell. This was a truly fond memory of my Dad and his work.”

Here are some pictures of the gun powder “grains” made during the Korean War at the Indiana Ordnance Works where Joe McNeil’s father worked.

Above is the display case with the different powders manufactured at the DuPont plant. They include: 37 MM/AA, 75MM Pack Howitzer, 50 Cal. 5010, 20 MM 4831, 30 Cal. 4895, 76 MM, 3″, 5″, 90 MM, 4.7″, 240MM, 8″, 280 MM, 175 MM, 155 MM Howitzer, 155 MM Gun M.P., 8″ Gun M.P., 12″, 14, 16″. There are different-sized ‘grains’ for specific rounds.

16-inch/50-caliber gun projectile plus six propellant bags. Display mockup aboard U.S.S. Iowa (BB-61) in San Pedro, CA. Photo by James Madison per Creative Commons CC-BY-SA-4.0 license.

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.

Learn More with FREE Vihtavuori Reloading APP »

This article originally appeared on the Vihtavuori Website.

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).

So how does powder grain 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.

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.

Learn More with FREE Vihtavuori Reloading APP »

This article originally appeared on the Vihtavuori Website.