Jim,
I think you are spot on in all cases here for what little I know. I speak with the desire to learn more and not that of any authority.
I would love to hear from all who have any knowledge in this. I agree it is hard to draw any conclusions with what we have from the mid 18th century time frame. I just do not see a vast amount of full blown gunmaking going on here until that pivotal point mentioned. I would think if any piece needed to be made here it was cast as is evidenced by later surviving examples and period remains of casting setups. Casting for a gun shop here would certainly not have needed such a large industrial process. I think that although there are only a few decades between this time frame and the period where we have examples, they are different in circumstances as night and day.
As far as the mid grade and lower mid grade fowling pieces, from what I have seen from archaeological digs, manuscripts such as store inventories and orders as well as surviving pieces, they were cast. It was just more economical to cast if any from of elegance was the intent. We are discussing the oncoming of common brass items beginning in the late 17th century on another forum. The industrial process seems to begin in both England and the continentals at that time.
Some trading gun common parts (English) are indeed somewhat primitive in comparison. Strappy things with crude engraving. Some were also cast but the sheet pieces (as well as the sheet itself) were produced across the pond in an industrial environment developed for that procedure which justified it's economy I guess.
Diderot's shows brass being poured in large sheets and then pressed. It was then cut into smaller sizes of sheet which could be trip hammered, wrought out for making wire, strapped, etc. Access to this sheet over there was an economical alternative if quick and simple mounts (such as a quick and dirty strap type guard) were to be done.
I do not know offhand if sheet was sent over here. Maybe Mr. Brumfield or someone else can elaborate on that. For any production over here it seems casting is the way it was done from both a practical view as well as historical.
I believe Williamsburg has recovered some lead patterns used to make harness buckles and I would guess that same procedure to be good for hardware.
bgf,
As i mentioned above, lead patterns could be used as "originals" to cast from. Maybe Gary or someone else can clarify if mounts were done in the same manner.
Dont you hate it when you ask for historical information and then you get a response as to how someone is doing it in present day? Well I am about to do the same.
My buddy is experimenting and having good results with making an initial wood pattern which is easy to work and detail, then casting a lead pattern from it for regular use with minimal shrinkage.