If you are able to make up/get made a suitably pinned and angled tool but it still doesn't budge try the following.
Using lead or fibre jaws to protect the action, rigidly clamp the action in the machining vice on a solid drill press or vertical mill, paying attention to the actual angle of the DSSD in the breech face, not the breech face itself.
Place your newly made and perfectly fitting tool in the chuck so that it bottoms-out within the chuck and tighten the chuck firmly.
Align the tool bit with the suitably angled action and lower the tool into the pin holes. Lock in this position or have a friend lean on the press arm. Turn the tool with a spanner or whatever (not power).
This is an excellent way of removing frozen pins from actions, especially when the slots have become mashed as it stops the turnscrew climbing out of the slot while torque is applied.
