My Uberti 1876 is leaving a scratch along the length of the cases, and I suspect the tab on the bottom of the breech bolt needs a little filing. I have a 1873 takedown guide, which is very similar, and they instruct you to drift out the front link pin and remove the firing pin extractor in order to remove the breech bolt. I've been wailing on the pin, properly supported, quite heavily, and it will not budge. I fear I'll destroy something. Any suggestions?