I have used the Nightforce BR for BR last year and now using a Weaver t36 as much lighter etc.
Re the mag if you shoot in Light or Heavy Varmint class then the mag is open and not limited to 12x.
If you only want to shoot in Sporting class then you could look at the smaller Grand slam weaver or similar, they do a target fine cross hair and 1/8 mildot centre which I have used for BR in the past. Nice scope. Bushnell elite 6500 are good glass for the money also, but not sure of availability of target ret on them.
Leup Mk4 could be an option second hand as well.
If you decide to let your sightron go I would be interested as want to upgrade my FT rig from the Nikko's
FTP900 +Sightron S111 10-50 x 55
AA Pro Target in FWB FP70 stock + MTC Mamba lite
Daystate Airwolf + Bushnell Elite 6500
" life is about the memories we hold and not the things that we own"