After a bit of research
, I finally found the article on pillar bedding, written by Kelly McMillan, about 5 years ago.
"I think I can speak to this issue because my father, Gale McMillan was the originator of the practice. It came out of necessity and had nothing to do with accuracy. In the early days of fiberglass stocks, both Brown Precision Stocks (the originator) and McMillan Stocks were made using the lightest material we could find. As a result, both had a similar problem. Brown used polyurethane foam to blow out the cloth against the mold, and because they molded their receiver area and barrel channel's in, there was foam under the action. We used a very light filler made of epoxy resin and micro balloons. With both stocks you could crush the material between the receiver and the trigger guard by tightening the guard screws. The more you tightened, the more the receiver would move and the more your shots would wander. To solve this problem, my father would drill the guard screw holes out to 3/8". He would wax the screws up and then let the bedding material fill in the hole around the screws during the bedding process. After the bedding material set, he would drill the holes out just slightly bigger than the guard screws so the pillars were made of bedding material but they were dense enough to stop the receiver area of the stock from compressing. Eventually, we found aluminum pillars to be easier and just as effective, so we switched".
"Word spreads fast in the BenchRest community, and soon everyone was pillar bedding. Today, we refer to it as state of the art. But, technology and materials have changed over the years and all but our EDGE Tech and benchrest stocks have a dense enough material in the action area that using normal torque settings on the guard screws the material will not compress at all. Gale was the first to glue a benchrest action into a rifle. The Marines tested the stocks we made for them under 100 lbs of torque and got less than .0001 compression on the receiver area. We recommend 45-50 inch pounds on the guard screws".
"One last thing…. pillars do one thing and one thing only, stop compression. They don't increase accuracy or reliability and they don't allow you to remove and replace the barreled action any more often without degradation of the bedding. If a McMillan stock is bedded properly using a good compound, like Marine-Tex, pillars are unnecessary. So why do we use them? Because it's state of the art, and that is the way people expect it to be done".
