My first build from a kit was a S-F kit. I ordered it without a lock, nor inlet and put a Caywood lock on it. I know for a fact that some of the parts are from the Mold & Gun shop and the stocks are from some of the same stock places that Track & orher kit builders, less Chambers, use.
But you MUST KNOW (and research) what you’re buying in regards to design or school. Plus Ray will work with you, and you can upgrade the barrel, lock or wood. His basic barrels are from DOM tubing, but if you read the detailed technical report on those ‘dom’ barrels as posted on the site, then you would have no reservations using one, less that you might want a premium barrel.
One difference for example, would be that the breech on a ‘basic’ barrel would be parallel, before the wedding band transition ‘step down’ to the tapered round barrel, whereas on a premium barrel, the breech length would be tapered.
Thus those ‘basic’ barrel & lock components is why his kit is $600 and a ‘similar’ kit from another supply house would be $800 to $900 or more. If your budget is tapped out at $600, buy the S-F kit with the caveats noted, else save up and buy a $900+ Chambers kit or the $1K Kibler kit. I personally would not buy a “built” rifle from S-F, but you can certainly build a usable arm from their kits.