HS Precision places the aluminum bedding blocks into their stocks but McMillans are fabricated in an entirely different process and there are no bedding blocks. The McMillan heavier stocks utilize aluminum or steel pillars, round pieces of tubing that help ensure the stock does not crush when you torque the stock bolts and essentially give the barreled action something to sit on, besides the bedding that should be used. In fact most McMillans are bedded with a special compound that makes for a perfect fit of the receiver into the action area of the stock and the pillars are glued in place at each stock bolt hole. They must be of proper length to support but not too long or the action will not seat properly.
The aluminum bedding blocks work but they work best when a slight amount of bedding compound is placed in the receiver area to make a perfect fit of the action into the action area of the stock. This is called skim bedding and it is highly recommended by HS. I believe HS originated the idea of the aluminum bedding block, theirs goes inside the pistol grip and extends to about where the barrel screws into the receiver. One long piece of CNC'd aluminum.
McMillan has the best stock bedding specialist in the industry on staff and he does incredible "full action to the end of the barrel channel" bedding. His work is amazing, not cheap but worth every penny.
