Over the last year or so I started shooting HighPower, and had my Rem700VS tooled up for XTC. The loads that I found worked well in it were Nosler J4 155gr, Lapua cases, CCI BR2 (and Fed 210 GM) primers, and 43.0 gr of Varget for the 200/300 sections. For 600yds I was using 47.5gr Varget, everything else the same. Fairly hot load, but actually *less* than what Nosler has in their latest loading manual (48+). Shot very well for me.
HtH,
Monte