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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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February 3rd, 2020

Rear Sand Bag Tuning — Fill Levels, Sand Types, Bag Designs

With the Berger Southwest Nationals (SWN) taking place this week in Phoenix, we are reprising this discussing of rear bag designs and fill levels. By “tuning” your rear bag you can reduce hop on shot-firing and help your rifle track better. All that can translate to better scores, particularly with large-caliber rifles.

Tuning Your Rear Sand Bags

Over the years, noted gunsmith and a Benchrest Hall-of-Fame inductee Thomas ‘Speedy’ Gonzalez has learned a few things about “tuning” rear sandbags for best performance. On his Facebook page, Speedy recently discussed how sand bag fill levels (hard vs. soft) can affect accuracy. Speedy says you don’t want to have both your front and rear sandbags filled up ultra-hard. One or the other bag needs to have some “give” to provide a shock-absorbing function (and prevent stock jump). And you want to tune your fill arrangements to match your shooting style. Free recoil shooters may need a different fill levels than bag squeezers (who a softer bag but harder ears).

SAND BAGS & HOW TO FILL THEM by Speedy Gonzalez

I was asked several times by competitors at the S.O.A. Matches and F-Class Nationals as to how I fill my sand bags for benchrest competition. Here is a copy of a reply I gave several years ago:

Back in the old days, Pat McMillan told me: “You can not have two bags filled so hard that you gun bounces on them in the process of firing round at your target, especially if you have a rig with a very flexible stock. The bags must be set up in a manner for them to absorb the initial shock of the firing pin moving forward and igniting the primer.

Then [they must] maintain their shape and absorb the second shock wave as well the rearward thrust and torque of the rifle. What happens to the rifle when this is not done? Well let me tell you. The rifles have a very bad tendency to jump and roll in the bags. This causes many of those wild, lost shots that one can’t explain.”

Here’s some Good General Advice for Bag Set-up:

1. You should not have TWO hard bags [i.e. both front AND rear] in your set-up.

2. Heavy sand magnifies these phenomena.

3. If you are a bag squeezer, pack ears hard and leave bag pliable enough to squeeze for the movement required. You may pack front bag as hard as rules permit.

4. Free recoil shooters pack both bags firm, but not so hard as to allow stock jump. Especially if you have a stock with a very flexible forearm.

5. We use play-ground sand, also know as silica sand. I sift mine to get any large impurities out then mix it with 25% to 50% with Harts parakeet gravel to the desired hardness that I am looking for. The bird gravel keeps the sand from packing itself into that solid as a brick state.

Speaking of bricks — another thing that happens when shooters employ that heavy zircon sand is the ears form a low spot under them from recoil and then tend to rock back and forth with the rifle causing many low shots to crop up. Edgewood makes an Edgewood/Speedy rear bag specially reinforced under the ears to eliminate this scenario.

General Thoughts about Bag Construction and Ear Materials
I do not like the solid double-stitched leather bottoms. While this seems like a good idea, I see more shooters have problems because of them. They tend to slide around the bench and or slide with the rifle on recoil. The standard Protektor with Cordura rabbit ears and an Otto ring bag with a Cordura front would be what I would suggest to the new shooter or one of the Edgewood / Speedy rear bags, these mimic the “Donut” and feature a ring of leather around the bottom circumference that keep the bottom from rocking on the bench or ground[.]

One last note –If you use the Cordura bags, keep them sprayed with a good silicon spray or “Rain-Ex”. This keeps them from getting sticky. — Speedy

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