  We present a novel method for constraining the length of the Galactic bar
using 6D phase space information to directly integrate orbits. We define a
pseudo-length for the Galactic bar, named $R_{Freq}$, based on the maximal
extent of trapped bar orbits. We find the $R_{Freq}$ measured from orbits is
consistent with the $R_{Freq}$ of the assumed potential only when the length of
the bar and pattern speed of said potential is similar to the model from which
the initial phase-space coordinates of the orbits are derived. Therefore, one
can measure the model's or the Milky Way's bar length from 6D phase-space
coordinates by determining which assumed potential leads to a self-consistent
measured $R_{Freq}$. When we apply this method to $\approx$210,000 stars in
APOGEE DR17 and $Gaia$ eDR3 data, we find a consistent result only for
potential models with a dynamical bar length of $\approx$3.5 kpc. We find the
Milky Way's trapped bar orbits extend out to only $\approx$3.5 kpc, but there
is also an overdensity of stars at the end of the bar out to 4.8 kpc which
could be related to an attached spiral arm. We also find that the measured
orbital structure of the bar is strongly dependent on the properties of the
assumed potential.
