RE: Zeroing Scales
Briman makes a very good point. The measurement that you are loading to is relative. If your scale says 24.5gr and that is the load that shoots, it doesn't matter if it really weighs 24.3gr or 24.7gr.
Although most reloading scales are pretty good, the possibility of measurement discrepancies is another very good reason to NOT use loads that others post on internet forums as written without working up on your own. Who knows? Maybe the person that is posting the load has a set of scales that are .5gr off, one way or the other.