My range rods are just 7/16" dowel rods from the hardware store. I cap the bottom end with a .40 S&W cartridge case with the primer pocket drilled & tapped 10x32 to hold brushes or jags. It works vastly better than a skinny & slippery steel rod. I favor tight patch/ball combos and it would be impossible to load with a 5/16 steel rod except by pounding with a series of short up & down strokes. With a rod I can actually get a grip on I can run the load down bore smoothly with a hand over hand push without battering the front of the ball. They are so cheap I can afford to have several different lengths for different guns. I cut them a couple of inches longer than the bore and cap the top with a wooden ball, drawer pull or piece of antler. For those who believe a wooden rod will "wear out the muzzle", it was tested with a simple machine which ran a rod up and down the bore hundreds of thousands of times with no detectable muzzle wear.
