Thanks Doco and John for your replies.

I placed a few drops of Breakfree CLP into the plunger/spring and let it sit for an hour. I used a small slotted driver to lift it up into its recess. I noticed it moved further up than my earlier attempt. I heated it up using my heat gun until the CLP started smoking. After it cooled down I used my Panavise as to squeeze the safety back into the bolt sleeve as I lifted the plunger up. The plunger lifted up over the rim and sat down in its track. Success!

Thanks,
Mike