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April 10th, 2022

Sunday GunDay — How to Fill Sandbags & Fill Material Options

sandbag fill sand types

sandbag fill sand typesHow to Fill Shooting Sandbags Most Effectively
For both front and rear Edgewood bags, start by looking for the black nylon/cordura flap. This flap will have white stiches running along both sides. Note that the flap is actually two pieces of nylon/cordura which are sewn together. These two pieces must be separated at the end where there are no stitches in order to insert a funnel or other filling device.

Hold the bag so that the flap is pointed straight up and fill half way. Using a blunted rod and alternating between filling and packing, begin packing the sand firmly into the bag until the shape is uniform and you are satisfied with the firmness. Slam the base of the bag firmly on the bench several times to compact and evenly seat the sand. Then, check to see if more sand needs to be added. Repeat this process for the ears if you are filling a rear bag. Note that as the sand continues to condense during use, the bag may occasionally require additional sand until it reaches maximum capacity. NOTE: This tip is from Creedmoor Sports, which carries Edgewood Shooting Bags.

Edgewood Gater rear bag sandbag
Edgewood offers an innovative rear Twisted Gater bag with an unusual asymmetrical footprint. This provides arm/hand support for the shooter while still providing superb rear support for your bench rifles.

SANDBAG Fill Options — Yes Weight Matters

Weight benchrest sandFor most shooting applications, “heavy is good” when it comes to sandbags. The more your sandbag weighs, the better it will resist movement or mis-alignment that can throw off a shot. In order to increase the weight of their rear bags, serious shooters have turned to exotic sand formulations that offer greater density (hence higher weight by volume) than plain silica sand (aka “play sand”).

In this article, Jason Baney reviews three popular alternatives to play sand for rear sandbags. He tested each variety to determine its density, i.e. how much volume it would displace per pound. Then he calculated how much each type of sand would weigh in various sizes of rear sandbags: standard, large, and ultra-large (Bigfoot). Check our Rapid Reference Chart to see how much weight you can add to your sandbag by switching to heavy sand.

Is heavy sand worth the added expense? For serious shooters, the answer is yes. More mass equals more stability, and a more stable bag will help you shoot tighter groups. By switching from conventional sand to Zircon or Chromite, you can DOUBLE the weight of sand in your rear bag.

SEB bigfoot bag
Shown above are the latest SEB Bigfoot Bags. Note that the bags sit perfectly flat — there is no bulge on the bottom even though the bags are “packed to the brim with sand”.

Heavy Sand — Weighing the Benefits
by Jason Baney

Play Sand BenchrestMany serious Benchrest shooters fill their sand bags with “heavy sand”. This practice may seem “overkill” to most shooters, but its benefits are realized quickly when shooting from a bench. Heavy sand is more dense than normal silica “play sand” and therefore makes the sandbag heavier and more stable. How much heavier is the heaviest sand? Check the chart below and you’ll see that Zircon sand weighs essentially TWICE as much as ordinary play sand. More weight equals more inertia opposing bag movement, plus more gravity-induced “stiction” on the bottom of the bag. In other words, using heavy sand helps your rear bag stay planted on the bench during a string of fire. When you shoot a hard-recoiling gun, the difference between a bag filled with play sand vs. Zircon is very noticeable. The Zircon-filled bag stays put. The play sand-filled bag may not.

Rapid Reference Chart

Comparative Sand Weights by Sandbag Size
SandBag Type Play Sand Riverbed Sand Chromite Zircon
Standard 5″x6″ 5.1 lbs. 7.9 lbs. 9.9 lbs. 10.1 lbs.
Large 6″x8″ 6.8 lbs. 10.5 lbs. 13.2 lbs. 13.4 lbs.
BigFoot 6″x13″ 10.2 lbs. 15.8 lbs. 19.7 lbs. 20.1 lbs.
Weight Increase Compared to Play Sand
Zincon +98% Chromite +94% Riverbed Sand +55%

heavy sand sandbags

The Benefits of Heavier Sand

Heavy Sand helps your sandbag resist the tendency to shift or change alignment (relative to the stock) during recoil. This ability to maintain sandbag alignment is vital when shooting competitive Benchrest, either short-range or long-range. Having to fight a “migrating” rear bag during a group at 1000 yards will not do anything to help your accuracy. In non-competitive use, heavy sand can still benefit shooters. Friction from the stock on the rear bag, or bumping the bag on recoil with either a body part or pistol grip can move a lighter bag out of place and necessitate realigning the bag to get on target.

Of course there are some shooting situations where you don’t need (or don’t want) maximum sandbag weight. During a “walk-around” varmint session you may prefer a lighter bag. Beanbags that I carry around the groundhog fields stay filled with plastic beads, making the bag handier to tote. But, any rear bag used on a bench will be as heavy as I can make it while still using “sand” as filler.

Heavy Sand, Lead Shot, and Competition Rules

Some will say, “Well if you want a heavier sandbag, why not just add lead shot?” That is a great idea, but as far as I know, it is also illegal in every form of Benchrest competition. The material in sandbags must actually be “sand”, and only sand. It’s tempting to filter in a mix of shot and sand to increase weight, but that would also violate the rules.

Heavy Sand — Available Types and Properties

Heavy sand comes in several different varieties. In this article we tested three types: Zircon, Chromite, and commercial Riverbed sand (Exo-Terra brand “Reptile Sand”). All these are heavier alternatives to normal silica “play sand.” There are other types of Heavy Sand not tested here, such as Garnet Sand, which is between Chromite and Zircon in weight.

Sources: Sinclair Int’l sells black “Heavy Sand”, basically chromite. Large quantities of Zircon and Chromite are available from IFS Industries, and other industrial suppliers.

Sand Characteristics

Dupont Zircon M (pale tan): 165-175 lb/cu.ft; avg. particle size 0.01″.

Prince Minerals Chrome CAST 7850 (Chromite) (black): 172 lb/cu.ft; avg. particle size 0.02″.

Exo-Terra Riverbed sand (amber). Available at pet stores.

Silica “Play Sand” (tan or light gray). Available at Home/Garden stores.

Zircon and Chromite Sand

Riverbed Reptile and Play Sand

Zircon SandZircon — Heavy-Weight Champion
To my knowledge, “Dupont Zircon M” is the heaviest “sand” that a normal human can acquire. It is also the most expensive. Zircon is a very light tan/brown color and is very similar in appearance to normal sandbox “play sand”. Zircon is normally rated as having the greatest density among heavy sands and it has the smallest particle size, though some Chromite sand density values overlap the Zircon numbers.

1.00 pound of Zircon displaces 149cc vs. 295cc for Play Sand. So, that means Zircon is 98% heavier than an equal volume of Play Sand.

CONSUMER TIP: Real ZIRCON sand is TAN in color, not black or dark gray. Some “heavy sand” vendors promise Zircon but deliver a dark gray sand that is something else entirely!

Chromite SandChromite — Almost as Heavy as Zircon, and 30% Cheaper

Chromite sand is nearly the same density as Zircon but it costs quite a bit less. Chromite typically sells for about 25-30% less than Zircon (comparing bulk prices of both types of sand). Chromite sand is black in color. So when you buy “heavy sand,” make sure you are getting what you pay for.

1.00 pound of Chromite displaces 152cc vs. 295cc for Play Sand. So, that means Chromite is 94% heavier than an equal volume of Play Sand.

Riverbed SandRiverbed Sand — Weighs Less but Costs More than Chromite
Riverbed sand, is about 30% less dense than Zircon or Chromite, but is about 150% more dense than silica sand. Depending upon where you buy this sand, and the quantity, you will most likely pay more for this sand than you would Zircon or Chromite. Riverbed sand is a conglomerate of several different sizes and colors and appears red and black. Unless you are unable to get Zircon or Chromite, I would not bother with the riverbed sand.

1.00 pound of Riverbed Sand displaces 190cc vs. 295cc for Play Sand. So, that means Riverbed Sand is 55% heavier than an equal volume of Play Sand.

Density/Volume Testing and Weight Comparisons

All four sand varieties mentioned above were tested for volumetric density by weight. Each type of sand was weighed out to 1.00 lbs. on a commercial postal scale. Each 1.00 lb sample of sand was then poured loosely into a 600ml beaker and shaken minimally to level the top surface. This served to determine the volume that the sand occupied.

1.00 pound of sand displaced the following volumes:

Zircon: 149 cc
Chromite: 152 cc
Riverbed sand: 190 cc
Play Sand: 295 cc

How do the density-volume numbers translate to the real world? Here is an estimate of how much each sand would weigh in various sizes of rear bag:

Standard Bunny Ear Bag

5″ by 6″ footprint or about 1500cc

Zircon: 10.1 lbs.

Chromite: 9.9 lbs.

Riverbed Sand: 7.9 lbs.

Play Sand: 5.1 lbs.

Benchrest Sandbag
Protektor Doctor Bag

6″ by 8″ footprint or about 2000cc

Zircon: 13.4 lbs.

Chromite: 13.2 lbs.

Riverbed Sand: 10.5 lbs.

Play Sand: 6.8 lbs.

Benchrest Sandbag
Seb BigFoot Rear Loaf Bag

6″ by 13″ footprint or about 3000cc

Zircon: 20.1 lbs.

Chromite: 19.7 lbs.

Riverbed Sand: 15.8 lbs.

Play Sand: 10.2 lbs.

Benchrest Sandbag

Conclusions and Recommendations

What’s the best choice? For most users, we recommend Chromite. Chromite delivers nearly the same bag weight as Zircon but is more economical to buy. But for those who demand the maximum weight in their sandbag (without consideration of cost), Zircon is the top choice because it is sold at a finer grade (higher density) than Chromite. However, Chromite will save you money, and deliver very nearly the same amount of weight by volume. When purchased in bulk, Chromite is typically 25-30% LESS expensive than Zircon.

Reptile SandI would not suggest using the Riverbed sand unless you really need to fill a sandbag immediately and can’t wait to locate a source for either Zircon or Chromite. Keep in mind that Sinclair Int’l and other major mail-order vendors do sell heavy sand (though Zircon and Chromite may be much less expensive when purchased in larger quantities from local industrial sources.) The price of the Riverbed sand will vary quite a bit depending on the pet store and quantity bought. The Riverbed sand I tested, Exo-Terra Reptile sand (photo right), was fairly expensive as purchased at a pet store.

Bottom Line: When it comes time to fill your new rear bag, you may want to save a few dollars and go with cheaper Chromite sand, but if you want to gain every bit of weight possible, step up to the heavier Zircon.

Lenzi Rear Bag
Lenzi Rear bags work very well and are popular with top competitors. This are sold through PMA Tool.

TOPICS: Sand, Heavy Sand, Zircon, Dupont, Chromite, Riverbed Sand, Reptile Sand, Beach Sand, Play Sand, Benchrest, Protektor, Edgewood, SEB, BigFoot, Gator, Docter Bag, Doctor Bag, Loaf Bag, footprint, leather bag, Rear bag, Sand Density, Silica, Exo-Terra, IFS Industries, Sinclair International.

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April 10th, 2022

TECH Tip: Powder Grain Shapes — What You Need to Know

Vihtavuori loading propellant reloading powder N133 N150 N140 N550 ball flake stick extruded perforated powders

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.

Vihtavuori loading propellant reloading powder N133 N150 N140 N550 ball flake stick extruded perforated powders

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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Vihtavuori loading propellant reloading powder N133 N150 N140 N550 ball flake stick extruded perforated powders


This article originally appeared on the Vihtavuori Website.

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April 10th, 2022

Reloading Die Maintenance — When and How to Clean Your Dies

Hornady Die cleaning

After purchasing a new set of dies from Forster, Hornady, Redding, or Whidden Gunworks, you’ll want to disassemble the dies, inspect then, and then remove the internal grease and/or waxy coatings placed on the dies by the manufacturer. Below are two videos that show how to de-grease and clean dies as they come “out of the box” from the manufacturer. The videos also explain how to clean your dies after regular use. Cleaning your dies helps remove carbon, brass shavings, lube residues and other stuff that can get inside the dies.

In the first video, from Creedmoor Sports, Bill Gravatt (Creedmoor’s President) shows various methods for cleaning dies both when new and after they have accumulated carbon and lube after use. This video is definitely worth watching. In the second video, a Hornady technician shows the method for degreasing dies before first use. A convenient aerosol spray cleaner is used in the video. You can also use a liquid solvent with soft nylon brush, and cotton patches. NOTE: After cleaning you may want to apply a light grease to the external threads of your dies.

Creedmoor Sports Die Cleaning Video with Bill Gravatt

Hornady Video Showing Aerosol Cleaner

Clean Your Sizing Dies and Body Dies Regularly
These same techniques work for cleaning dies after they have been used for reloading. Many otherwise smart hand-loaders forget to clean the inside of their dies, allowing old case lube, gunk, carbon residue, and other contaminants to build up inside the die. You should clean your dies fairly often, particularly if you do not tumble or ultrasound your cases between loadings. It is most important to keep full-length sizing and body dies clean. These dies accumulate lube and carbon residue quickly.

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