Not to mention the cost of the McMillan action, plus the crappy Canadian dollar rite now, and the cost of import fees. Put that together and i bet you could buy a PGW 50BMG mag fed action for less money and have it much sooner!!!
When you can buy a complete PGW mag feed 50BMG in a very nice and tactical cadex chassis for around $8,000 why even bother trying to get in a McMillan action. Also you can get the PGW actions in single shot if you like.
My last custom 50BMG when it was all said and done, I could have bought two STEYR or Barrett rifles and a scope for less and saved the 12 month build time!!!