Jim - there is a lot of misinformation out there if you base your decision on what some of the kit suppliers websites and catalogs tell you. There is getting to be better information out there - Jim Chambers gives good descriptions on their website.
And as the other guys pointed out, it depends on where and when within Virginia.
There are quite a few surviving brass mounted rifles believed to be from the 1770-1780s from the areas of Virginia from Rockbridge and Augusta Counties on north, over into and down the Shenandoah Valley. You would be safe going with brass mounts for a rifle like this.
For iron mounted guns, there are a number of guns with iron mounts (most with stepped wrists) that are believed to have been made in southwestern Virginia that look to be from the 1790-1800 period. (Or call it the Appalachian region, etc. possibly as far north as Botetourt County and the James headwaters area to as far south and west as Tennessee - remember East TN was settled beginning in the late 1760s and there are references to guns being made there by around 1790 if not earlier.) Unfortunately, the examples I know of are not signed. There are some of these surviving guns that show some makers worked in iron or brass - that is, unsigned iron guns and brass mounted guns that look strongly like they came from the same shop. For what it's worth, iron furnaces began to pop up a lot in that region beginning in the 1790s, although that just may be a coincidence.
There are a few other iron mounted guns that have earlier looking architecture, but few strong regional style clues, like the iron mounted piece in RCA or the "Old Holston Gun." They are suspected to be from the region and to pre-date 1790 by some.
So for an Appalachian region gun, 1790s and later, iron or brass mounts are probably correct. Earlier? Maybe a few iron, but who knows? I suspect they didn't wake up in 1795 and invent iron mounts all of a sudden so I believe there were a few around - the style or preference originated somewhere. But that is just my opinion. For other parts of Virginia, and the pre-1790 era, I would go with brass as the surviving examples really strongly indicate that.
Guy
