Aluminum Bedding Question

[CEYoung2]

I recently swapped my laminate Ruger M77 Mark II stock (.30-06 w/ 1:10" twist) with a new Hogue replacement. The Hogue stock is the full aluminum bedding block version. Previously the rifle would group 180gr. Nosler AccuBonds around 1-1/2" @ 100 yards and now they're about the size of a softball. 150gr. ammo of most brands seems to shoot better than ever. Even the cheap Remington stuff is under 1". I'm new to learning about ballistics and barrel harmonics so I would appreciate if someone could explain: Why would the rifle stop grouping 180's and tighten up on 150's with a solid bedding foundation? Isn't that more of a function of the barrel twist?

 

[JDGray]

Be sure the barrel is free floated, and also make sure the recoil lug isn't bottoming out in the new stock, binding things up as you torque the action screws.