I have some historic UTM coordinates as NAD27 (556787, 7169250) which I entered into a spreadsheet and have imported into QGIS.

I assign them the projection Nad27 / UTM zone 12N (EPSG: 26712)

I save as... Projection Nad 83 /UTM zone 12N (EPSG: 26912)

When I compare coordinates, the coordinate shift is different than what I know it should be (in particular, there is no east-west component to the transformation), and when I use a separate NTV2 transform there is a shift of ~ 30m north, 50m west.

I have looked at This help article which involves projecting across UTM zones, which I am not doing.

and This other help article which is solved by using a more robust version of the nad27 projection (EPSG: 26712 instead of EPSG:2027) which I am already doing

Am I missing something very simple here?

I am running QGIS 1.8.0 on window

I have some historic UTM coordinates as NAD27 (556787, 7169250) which I entered into a spreadsheet and have imported into QGIS.

I assign them the projection Nad27 / UTM zone 12N (EPSG: 26712)

I save as... Projection Nad 83 /UTM zone 12N (EPSG: 26912)

When I compare coordinates, the coordinate shift is different than what I know it should be (in particular, there is no east-west component to the transformation), and when I use a separate NTV2 transform there is a shift of ~ 30m north, 50m west.

I have looked at This help article which involves projecting across UTM zones, which I am not doing.

and This other help article which is solved by using a more robust version of the nad27 projection (EPSG: 26712 instead of EPSG:2027) which I am already doing

Am I missing something very simple here?

I am running QGIS 1.8.0 on window