Re: Flatest shooting cartridge
I would go with a 300 mag necked to 6mm over the shorter cases like the WBY use Lapua cases and you will be good to go but in reality i would not use a 6mm. I would rather use a 25 or 6.5 The 264 Win Mag would be an excelant rifle for you and if you want more get up and go it can be rechambered to 6.5 Remington Ultra Mag with no troubles at all. You can use a Redding or Forster competition seater and run the Ultra mag reamer into it and then get a &mm Ultra Type S buching Full length Sizing die and use a bushing for a 6.5 case in it and you will have dies that fit the case well for a minimal expense over custom dies for an odd wildcat.
The best could be one of the Rem Sendaro II's in 264 Win Mag rechambered to 6.5 Ultra or even left as is in 6.5 you can use Sierra MatchKings from 107gr to 142gr and i have a mate here in OZ that has a few thousand 155gr MAtchKings that are discontinued that would make it an awsone long range rifle for feral Pigs and other medium game.
If you went with one i would get it skim bedded with Devcon Steel and fit a larger recoil lugg, adjust the trigger ( Or Replace if it was not suitable) fit a Good Muzzle Break and a Nightforce 8-32 NXS with a 30moa base also when the rifle is fitted with the larger recoil lug and muzzle break re crown the barrel. If i was to do the work i would lap the factory Remington barrel before re chambering and crowning as it realy helps to smooth the bore and they run in better and foul less. You could also fit one of the Defensive Edge adjustable cheek Pieces.
I think the post is a little badly named as you do want a very flat shooting cartrige but it has to be practicle to carry in the vehical at all times and be light enough to deploy quickly with a bipod. I would personaly fit a larget bolt knob aswell but it would not be essential.
I would probably use a Harris S type swivel bipod with a Pod Loc on it and a rear Mono pod the reason is it will get shot over the bonnet of the work ute and the rubber feet do not scratch the paint up to much and they also dont slide off when the rifle is just siting there.