Barrels and stocks:
Here is a .500 Mbogo with B&C stock:
That McMillan stock is currently on a .408/.338 Lapua Magnum Unimproved, aka 10.4 Spiridon Moor,
that has a No. 6 McGowen Light Target contour.
Conclusion: I need to leave the plywood on the other .500 Mbogo and use a McMillan stock on the .500 Jeffery Procrastination,
aka .500 Jeffery-P.