Skimbleshanks,
This is a contradiction of terms since every 'highly respected' gunsmith I know is running about 6 to 9 months for a complete build, usually less if you supply the parts.
I only know of three gunsmiths in the last 25 years who have delayed clients for long periods of time and it was because they were trying to make ends meet and then go out of business. Bad business managers.
Have you had any contact or explanation from this person? How does he justify 6 years and most importantly, how do you justify waiting that long?
Getting your parts and money back should be as simple as telling this person that you want them back. If they try to delay you again, simply inform him that you have turned this over to the ATF and that they will handle it from here on out. Local law enforcement in his area can be helpful also.
There are a dozen or more trustworthy, competent gunsmiths who hang out on this board. If you are truly having a problem finding someone to trust I can supply you with a list to help you.
Regards.