What ever happened to mailing it a piece at a time? Send it in 4 separate packages. Frame, cylinder, grips, and trigger mechanism.
One of those pieces is classified as the actual “firearm” - the rest are just “accessories.”
You’ll still need an FFL to transfer the one piece that is classified as the actual “firearm.” In this case, it is probably the trigger mechanism.
On a revolver, the frame is the gun. It is the piece which requires FFL transfer. For most rifles, it is the receiver (AR’s it’s the lower) whatever actuates the ammo is the firearm.