Originally Posted by LouBoyd
The most accurate long range rifle will always be the one in the hands of a skilled shooter who knows how to dope wind in the conditions and terrain where the shooting is being done. The cartridge does matter, but it's less important than shooter skill. Even less important than that is the make and model of rifle given the rifles can achieve the same velocity with the same bullets and aren't complete junk.
While I'm a 7mm STW fan I don't know of any factory rifle which allows the shooting of low drag VLD bullets. The SAAMI case length is 2.850" and the cartridge OAL is 3.65. There are only a few factory bolt actions which will fit even the SAAMI OAL and that only gives 0.8" ogive space which is not sufficient for shooting heavy VLDs like the Berger 180s. There are fairly simple options to extend the magazine of some rifles (Wyatts for the Rem 700 for example) but that's no longer an "out of the box" rifle.
In my opinion "out of the box is" is the same as "inferior long range performance". The major manufacturers limit their rifles to shoot SAAMI spec ammo. The limitations come from magazine length, throat depth, and twist rate. Barrel length limits usable velocity. All of those are easily adjusted in a semi-custom rifle.
Good points, however if the OP is looking at Coopers, they aren't necessarily a true "out of the box" rifle although you can get them off the shelf. If he does get a Cooper it will likely be ordered, especially in the cartridges listed. When ordering a Cooper you can have twist and some other things customized. Or for a LR rifle He could order one from Len or a rifle maker such as Snowy Mountain Rifles.