I was expanding on your comment that not only does cup & core (C&C; i.e. jacketed lead) vs. mono-metal (generally copper or some copper alloy) with mono-metals being longer or a given weight that also the even within the same material/construction type that shape of the bullet comes into play. All of those factors impact length. The the spectrum with respect to shape would be round nose vs. typical spitzer vs. a VLD/ELD/RDF. Also as you mention, altitude has a factor as well as air temperature.
It is interesting when you compare stability calculators that Berger and JBM take a slightly different approach. Berger includes temperature and altitude and JBM only includes temperature. JBM also includes an option to input the length of any plastic tip which I believe gets deducted from the overall length. I assume this has something to do with the plastic tip effectively having zero weight effectively reducing length for calculation purposes.
