If you are weighing all of your powder charges to within plus or minus 1/10 of a grain, then you are as accurate as most guys who reload for varmint rifles. Many benchrest shooters using ball powders don't weigh each charge, but use very precise volumetric powder measures. The scale is only used to initially set the measure, and to periodically verify nothing has changed.
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If you have any doubt about the accuracy of either of your scales, it's easy to check them for calibration. RCBC and other companies sell reloading scale check weights. But a cheaper alternative is to just have a few rifle bullets of different weights weighed on a calibrated analytical balance scale. Then scratch the actual weight on the jacket and keep them with your scales.
I did that when I was in college and used a Mettler H15 analytical balance we had in my organic chemistry lab. That thing was so sensitive that it could measure the difference between a bullet cleaned with acetone, and the same bullet with a fingerprint on it. You could probably get a Pharmacist to accurately weigh a few bullets, and convert from hundredths of a milligram to hundredths of a grain.
