You should be able to get a replacement firing pin from
www.e-gunparts.com as well as the buffer in case the oil bath doesn't do it any good. It sounds to me that the original parts weren't heat treated very well, you might replace all the parts and they end up being the same way. I would suggest checking to see if the parts need to be rehardened to help alleviate some of the hammering affect you are getting. Good luck with it.