The issue is the handle. The standard Defiance bolt handle requires a custom inlet in the stock or Chassis for the bolt handle. The Defiance bolt handle is Wider. You need to use the Modified Defiance Handle which will have the same inletting as a Rem 700.
If you have a standard Defiance bolt handle you will need to have the chassis machined back or get a new bolt from Defiance with a Modified Defiance handle.