Fine, but if you shoot a very hot load with 40 grains, I have been told the copper jacket will spin off and the bullet will come apart. As far as accuracy goes, its more of a bullet profile issue than a weight issue. In DCM competition, we shoot 52 grain BTHP Sierra bullets at reduced course, 100 yards, with excellent results using 1:8 barrel twist.
As an example, I also have a Ruger Varmint .223 that has a 1:12 and will shoot some heavy bullets very well for certain profiles. However, some bullets of the same weight with different profiles will keyhole the target at 100 yards, like the 62 grain green tip NATO.