Usually there has been a release agent (carnuba wax or even celophane) applied to the underside of the barrel/action/block that allowed for removal of the lock/action/barrel from the stock. We would use car wax (turtle wax) when doing a bedding job on a rifle.

Maybe check with the smith who glass bedded it in the first place, but I can't see epoxying a rifle to the stock without a way to separate the two main pieces.