by Glen Zediker
Most reloaders are going to invest in a powder meter. And, right off, it is a meter, not a “measure.” Meters don’t measure. My preference would be to most accurately call a “powder measure” a “dispenser.” That’s what it really does. The “measure” is comparing a meter hopper volume to a weight on a scale. This may seem tediously technical, but I think it’s important to really understand what we’re doing when we use a powder meter. It’s a volume, not a weight. The volume corresponds to a weight, that we arrived at through adjusting the meter volume.
If you plan on relying on a meter to throw charges, and not weigh each one, you best get a good meter. If the meter is only a starting point, where you are then going to use a powder trickler to top off a scale-weighed charge, meter quality is of no real concern. A powder trickler is a device that delivers propellant a kernel at a time.
So what’s a “good” meter? Good question. The very best have Culver dispensing mechanisms. Named for Benchrest pioneer Homer Culver, these precision-made mechanisms click, just like a back sight. Each click, of course, either expands or contracts a void that the propellant fills. The only Culver-equipped meters I know of are produced by smaller shops, and they are more costly. But unlike most of the major-player meter designs, a Culver setting cannot change. There are no set-screws or rotating micrometer stems or barrels. A lot of folks give advice to “check the meter each 10 throws….” Meaning, check to see if it’s still throwing the desired weight (by the way, that would be a pretty bad meter). My experience, which has come from a whopping lot of testing, showed me that my scale was going to change before a Culver would change.
If you look at how a meter works, there’s a volume-adjustable cavity that rotates in position under the propellant supply, fills with propellant, and then rotates back, to dispense the propellant through an outlet. When it rotates, the granules contained in the meter are struck off, fixing and sealing the amount of propellant in the “hopper,” I call it.
A few things: One is that the smaller the granules, the more precise each fill can be. Longer-grained kernels have more air space and “stack” more than smaller-grained kernels. It’s also clear that the higher degree of precision on the internal sliding surfaces, the more “clean” the strike-off will be. It’s also clear that meter operation has a lot to do with the consistency of filling the hopper. Just like tapping a case bottom settles the propellant to a lower fill volume, same thing happens when filling the hopper in a meter.
A key to good throws is working the meter handle consistently, and also settling on a contact force when the meter handle comes to a stop in the “fill” direction. It should bump but not bang. I wish I could be more clear on that, but it’s a feel that must be developed. Don’t go too slowly and gingerly take the handle to its stop, and don’t slam it there either. You want a positive, audible “thunk” when the handle stops. If it’s the same each time, fill consistency will improve. I have found that focusing on operating the handle at a constant rate of speed teaches this. It’s a positive movement that, for me, takes about one second to lift the handle.