There's no reason you cant have an accurate lightweight long range rifle, I have many in my safe's downstairs that fit into this category, you just have to treat the rifle at the bench for what it is, an ultra lightweight backpackers rifle in the 6-7.5lb range scoped usually will have a very thin contoured barrel and they heat up quick by a 3 shot string, depending on the size of the cartridge some quicker than others !
Generally in a hunting rifle of any weight you will rarely ever shoot more than twice at an animal....nevermind 3 shots so bare this in mind when your at the bench trying to shoot a lightweight rifle as if it was a heavy barrelled target rifle, keep your shot strings to 3 shots and or let it cool if your wanting to shoot a longer string......simple.
I have a Kimber Montana 84L chambered in the new 6.5 RPM which is basically a beltless 264 win mag for powder charge comparison, it has a 24 in #2 contour Benchmark barrel with Talleys and a Zeiss V4 4-16x44 scope and weighs 7lbs 3oz and does not have a brake,
I have shot it out at 800 yards without issue hitting a 12x12 inch steel plate shooting 156gr Berger Elite Hunters at 3070fps.
As far as lightweight rifles go if you buy a new Kimber Mountain Ascent take it to your gunsmith and have the action bedded, trigger lightened and ensure the mag box is not binding on the action when its tightened in the stock, I know it sounds crazy to do this to a new rifle but it could save you a lot of unnecessary grief down the road, and for the $100-$150 bucks spent its well worth it to do this to any rifle.
As far as a Fierce rifle's Ive never owned one but I have several friends with them, for the most part are accurate, all but one of my friends has had problems with their rifles, ejection issued, mag box issues, accuracy issues, of course I know a fellow that bought a $14,000.00 Gunwerks package that wouldn't shoot under 4 inches either so no matter what they cost they all can have issues, I had the same with a Weatherby Mark V Outfitter Range Certified Rifle, wouldn't shoot less than 4 inch groups with factory or handloads and that was supposed to be test fired from the factory ???
I have a Kimber Mountain Ascent 270 Winchester I won at a WSS of BC function, it weighs 6lbs 6oz scoped with Talleys a Leupold VX3 4.5-14x40 CDS 1" inch tube scope, shooting Barnes factory 130gr TTSX ammo its very accurate, and yes I had it bedded and trigger adjusted and the mag box freed up.