found a free (gpl) program called 'graph' at
tuned it to plot range of powder weight at given o.a.l., as given by various sources of load data.
two objectives are:
..visual presentation for comparison of data from various sources;
..identify set of points (o.a.l. and powder weight) for test loads.
for this purpose, treated as equal all bullets of near-same-weight and identical bearing surface. (e.g. 9mm bullets of 124 to 125 gr weight and copper jacket would be included, regardless if source recipe were for jhp, jsp, fmj, etc.)
where data source specified only a max powder load, i used 0.9*max as the starting load.
indeed, as one would hope to see, those powder ranges on the heavy side also specified longer o.a.l. (and vice-versa). i expect the plots to visually define an envelope within which to work.