We've played around with a few different methods for building your own sandbags at The BTG, and finally settled on this method as our most reliable and durable setup that doesn't leak dust or sand. If you use a duffel bag, you can build this for about $40 or so. If you want a slightly more versatile bag with handles along either side (for cleans and other movements), you can order a sandbag shell from Mountain Tactical Institute, but it will more than double the cost.
Using wood stove pellets for your filler rather than actual sand gives a much better volume to work with - I.E. because they're less dense than sand, the bag is physically larger for the same weight, which makes it more useful. For most of our bags, we used a whole 40-pound bag of pellets, and found that pretty much everybody in the gym can handle that weight for the movements we do. The 60 pound bags we made are pretty challenging for our bigger/stronger athletes, and the Rothco duffel bags we used should be able to accommodate up to 100 pounds of pellets for when we want to get really crazy.
The 3-Mil Contractor Garbage bags keep all the pellets and dust inside, while the 7-Mil "Demolition" bags with their fibrous construction prevent finger grabs of the bag from puncturing the 3-Mil liners.
We've also tried the "Ultimate Sandbag" products, and honestly we like these WAY better. The handles, snaps and zippers on the Ultimate Sandbags were pretty much just a pain in the ass most of the time, so we stopped using them. These DIY bags are much better!
Rothco 21x36" Heavy Duty Canvas Top-Load Duffel Bag or MTI Sandbag Shell
3-Mil Contractor Garbage Bags (Home Depot)
7-Mil Contractor "Demolition" Bag (Home Depot)
Heavy-Duty Zap Straps and/or Heavy-Duty Self-Wrapping Velcro Strapping
Wood Stove Pellets (Canadian Tire)
- Fill one of the 3-Mil Contractor Garbage Bags with as much wood stove pellet filler as you like. While bagging your filler in smaller pouches (E.G. 20 pounds per bag) could allow you to modify the weight easily, we've found that a single mass of filler works better for most movements because the bag is less floppy.
- Stand the bag up on end so the pellets settle, fold the excess bag over and press out any excess air. Make sure to spread the volume out so that the bag will fit inside the duffel bag or sandbag shell you're going to use in a manageable shape - it shouldn't just be a big lump/ball. Tie the bag closed with a double knot, then wrap the excess bag around the filled part (not TOO tight or the bag will rupture when used, but not too loose either) and secure it with duct tape. I do a double-wrap of duct tape around the length of the bag, and then three double-wraps around the width.
- Drop your filled bag inside another 3-Mil Contractor Garbage Bag, press out any excess air, tie the bag closed and secure with duct tape.
- Drop your filled double-bag inside a 7-Mil Contractor Garbage Bag, press out any excess air, tape the end closed (these bags don't tie well), then secure the whole thing with duct tape.
- Drop the filled, triple-bagged assembly inside your duffel bag or sandbag shell, and tie off the excess shell with either zap straps or self-wrapping Velcro strapping. We FAR prefer the Velcro strapping because it is less likely to snag or scratch you during use, and the strapping itself will fatigue less quickly than a plastic zap strap. Only downside to the Velcro strapping is it's a tiny bit more difficult to fasten it tight enough than a zap strap. If you use the Velcro strapping, we do at least two full, continuous wraps around the neck of the duffel bag/shell. If you use zap straps, use at least two to give yourself a backup in case one fails, and you may want to wrap the zap straps with duct tape.