I went through a similar exercise a few years ago for an across the course rifle and ended up with a sako varmint in .260 Remington. Not something I would recommend for a new shooter though. .308 allows you to compete in F-TR where you can be very competitive with a production rifle as opposed to F Open where you will be at a significant disadvantage. The Varmint rifles have a bit more weight to them which makes them easier to shoot well (particularly for targets) and more so with a sling. .308 ammunition is available in every firearm store in NZ and once you have a source, factory 308 target ammunition is available as well (Lapua, Norma, etc...).