  Although 2011 marks the 50th anniversary of Nb3Sn as the first high field
superconductor, real understanding of its upper critical field behavior
{\mu}0Hc2 is incomplete. Here we show surprising {\mu}0Hc2 data on highly
homogeneous bulk samples examined both by small-current, transport and by
volumetric-averaging specific heat and the reversible magnetization techniques,
which exhibit identical upper critical field {\mu}0Hc2(0.3 K) ~ 29{\pm} 0.2 T
with or without undergoing the cubic to tetragonal transition, a result in
strong contrast to widely used multiple-source data compilations that show a
strong depression of {\mu}0Hc2(0K) from 29 T to 21.4 T in the tetragonal state.
