Read and reread this thread...here goes.
To start, 600 yds is to far to be shooting at a big game animal, period, with near anything that is considered a sporting rifle. It can be done, folks do it, but it's a stunt. Wind alone will make good bullet placement difficult, much less range estimation, posture of the animal, etc, etc,
My understanding of the VLD huting bullet is that it enters, dumps and is not necessarily intended to exit. The reviews on the larger calibers and the VLD hunter are pretty postitive. But....... Using such a theory on a .243 may be flawed logic. The .243 may well enter and dump w/o the attending technology. You have actually used the slug and are getting exits. I dunno.
I hunt the .243 a bit, as does now my boy, and am not a basher. But I think the caliber is the ideal candidate for a premium bullet like the Patition, the A-frame, bonded technology, mono technology, etc, that is designed to expand, but hold together and penetrate. All those bullets, in the 100 gr range, will carry plenty of energy and shoot flat enough to bag deer to 300 yds + which is about as far as most will shoot game, especially whitetails.
The .243 is enough rifle, but proper bullet selection makes it even better.