I would continue to try to open the bolt like before. If the spent case remains in the chamber after getting the bolt open, remove the bolt and tap out the case with a rod and a wood or rubber mallet. Then run, don't walk, back to the gunsmith and have the chamber cast. Remember that a lot of these rifles were modified to shoot other cartridges after being surplussed due in part to the robustness of the M1917/P14.
Stuart