Will this work with my defiance anti-x SA action ?
Yes if your Anti X is a Rem 700 footprint action then it will drop right into this stock.
Will this stock fit a Bergara Ridge SP 6.5 Creedmoor?
You have this rifle correct? https://www.bergara.online/us/rifles/b14/ridge-rifle-2/. If so, yes this Trekker will fit your rifle. This stock is inlet for the Remington BDL floorplate which sits deeper than the Bergara floorplate so the inlet is cut deeper around the hatch that closes on the floor plate but this is purely cosmetic and your Bergara rifle will fit and function in this stock.
Will this stock fit a Christensen Arms Ridgeline 6.5 PRC short action with a Carbon Fiber barrel? Thanks
yes it wil.