A few years ago (December 1995 issue), we tested a Lyman Autoscale electronic powder dispenser and it didn’t work very well. The loads were always overweight; dangerously overweight some times. We think the problem was caused by the inertia of the beam balance scale, which was built into the dispenser.
The subject of this test is the RCBS PowderMaster, and it’s a winner. This electronic powder dispenser probably dispenses loads more accurately than you can weigh by hand. There’s no inertia problem because it uses an electronic scale. But the PowderMaster’s price is a little high—$214 plus the cost of the scale—and its speed is a little slow, compared to a volumetric powder measure. That’s the price you have to pay for accuracy.
The scale isn’t built into this dispenser. It uses a $203 RCBS Powder Pro scale which sits alongside the dispenser, catches the dispensed powder in its pan, and transmits a weight-measured signal to the dispenser. We tested this same scale (January 1996 issue) and rated it number one. At that time, it didn’t have the built-in data transmitting port (an infrared bulb on the side of the scale). If you have a Powder Pro scale, you don’t need to buy a new one. The scale manufacturer, PACT, will install an infrared transmitting port in your scale for $45.
PACT also manufacturers the powder dispenser for RCBS and sells it under their own name, too. If you buy the dispenser from PACT, which is the same price as RCBS, they will add the transmitter to your old RCBS scale for nothing. (Make the arrangements before you buy. Call 1-800-722-8462 CST). You can also buy what looks like the same scale, equipped with a transmitting data port, from PACT.
Setup and Use
Like other electronic scales, the RCBS Powder Pro scale needs to be calibrated before it is used; the procedure is explained in the instruction book. The book also recommends a 20- to 30-minute warm-up time before using the scale. (We didn’t find that much warm-up necessary.) There is no problem with the infrared transmission. If the powder pan is under the dispenser, where it could catch the powder, the infrared bulb is in the correct location. The pan supplied with the RCBS scale is plastic, but doesn’t hold a static charge that could cause powder to stick to it. The response time and minimum response of this scale are good. It’s a very good scale.
The RCBS PowderMaster powder dispenser also needs to be calibrated, to allow for scale lag, before it is used and each time the powder is changed. It takes about 8 minutes, but it is all automatic—you just push the button and wait. After it is calibrated for the powder being used, you just key in and “ENTER” the load you want dispensed, from 1.5 grains to 99.9 grains, and command “DISPENSE.”
There are two rotating powder delivery tubes in the base of the powder well. Powder delivery starts with the fast tube rotating at full speed, as the full load is approached the fast tube first slows to half speed and then stops. At this time, the slow tube takes over at full speed and shortly shifts to half speed, stopping when the load is complete. This is where the calibration and its exceptional accuracy come into play. Even at this slow rate of powder delivery, the scale lags the load by about 0.3 grain. Calibration has determined how much lag there will be and the dispenser stops that much ahead of time. If you want to read the actual load on the scale, you will have to wait two or three seconds for the scale to stabilize. Most of us frequently ignore this scale lag, but the dispenser doesn’t.
You can also use this dispenser as a power trickler to add a little more powder to a load that’s already on the pan. Just hold the “DISPENSE” key down and watch the scale. The problem here is the scale lag will catch you. Your load will be about 0.3 grain too high because the internal computer didn’t cut off the flow of powder a little ahead of time.
In our opinion, this dispenser is not a substitute for a volumetric powder measure. It’s much more accurate, but it’s way too slow. Extruded rifle powders are dispensed at about one grain per second plus an additional ten seconds per load, so a 45-grain load will take about 55 seconds to load the pan. Ball powders load at about the same rate. Flake powders will take about three seconds per grain, which we think is far too slow to be useful. You can speed the process up by pre-loading the pan with a scoop of powder that’s almost up to weight. The dispenser will take about 30 seconds to top off the load in that circumstance. That’s probably a little faster than you can do it manually.
A word of caution here. Both of these units, the PowderMaster and the Powder Pro, use a plug-in transformer to supply the necessary low voltage—9 VAC for the dispenser and 12 VAC for the scale. It’s important not to get them interchanged. The connectors on the ends of the cords are the same size and there is no unit identification on the transformers. The dispenser instruction book warns about this potential conflict, but the scale instruction book does not. Better mark them when you get them.
The scale has a limited lifetime warranty by RCBS, though PACT does the actual warranty work. The load cell, the delicate device that makes the actual measurement, is excluded from the warranty. It is also the component most likely to fail. PACT charges $45 for a load cell replacement.
Bottom Line
The RCBS PowderMaster is a little slow and somewhat expensive, if you don’t already have the required scale. But, this is the dispenser our testers have been waiting for. We highly recommend it.
