Gordon,
Not a good thing, but as King said if you load low pressure, low velocity loads and if you can see the difference in powders and skim most of it off, and mix it thoroughly you should be fine.
You didn't specitfy in your 15-20 drops as to what grains it might have been. In the lower grainage, up to 20 grs., there is about 7 grains difference between the two, and naturally the WSF is higher grainage. When it gets up around 30 grains WST to WSF the difference is close to 12 grains.
Also I would use this in modern guns proofed to todays loads and also use it in 12 ga where the mix would be less WSF.
Winchester would tell you to use it as fertilizer or dispose of it safely. They are not going to tell you it is okay for reasons of liability.
