I recently acquired a Stevens Tip-up rifle with a low 4 digit number. Its in bad shape cosmetically but locks up tight. I am in process of sleeving the barrel to 22 from 25 stevens and am going to have the action re-plated, new wood etc... I am having trouble finding a schematic. The only problem so far is removal of the firing pin, does it just unscrew? I have drenched it with liquid wrench and cant get it to move, but I don't want to bugger it up, any info would be helpful.