Savage's observations of how receivers move in their bedding during firing is the first I have heard mentioned. Actual observation of this movement changes things ... you don't have to guess or hope what might be going on anymore. If want to know what is actually going on, there is no substitute for direct observation. There is nothing like it to cut through BS.

Without such observations, there is no basis for hoping that the dynamics of receiver movement is a simple thing.

Since one of Savage's goals in this work is to have the receiver and stock recoiling as a unit, it seems unlikely they used a standard non-recoiling test rig for the observations.

Savage's claim is that AccuRails holds the receiver differently than other bedding blocks. There is nothing you have said which directly addresses that claim or the matter of direct observation of movement.

As for the cheap tupperware thing, I have been talking about a HSP with AccuRails versus without AccuRails as currently supplied, not AccuStock (see above).