Note 1: vinegar will leach out zinc from brass. Citric acid is safer.
Note 2: if there is less than 0.7gn from start to max (and charge weight is above 3.0gn), that tends to indicate a powder that is not a good choice. Generally, the pressure at the max is very spiky and they have had to drop the max charge so the max pressure does not exceed SAAMI. Generally, a good powder will produce a curve up to max pressure, while some powders like Clays and N310 will produce some sudden spikes and they have to take these short bursts of pressure into account. Of course, in ages past, such fast powders were only used for light target loads for 725-800fps and NEVER for max charges any way.
I have gotten sudden pressure spikes with light loads (well below max) with N310, TiteGroup, and Clays. I have never had that happen with AA2, Bullseye, Red Dot, Solo 1000, or 231/HP38--so I tend to stick with these powders.