FWIW, from Barnes FAQ:

Do I seat TSX bullets .030 inch to .070 inch from the lands, starting at .050 inch off the lands, as recommended with other X-style bullets?
Yes. All-copper TSX Bullets typically give better accuracy when seated off the lands and grooves (the rifling in the barrel).

I usually start at 0.050" off and continue seating in deeper increments. My .270 wsm shoots 130gr TTSX into tiny knots if given a long jump to the lands but shoots patterns close-up.