One needs to define intrinsically accurate".
IMO opinion the cartridge that is easiest to make shoot well is the 222 Rem. It was developed by Mike Walker a Remington engineer/benchrest shooter specifically for shooting small groups. It turned out that not only was it capable of shooting small groups but it does so with a great many powder/bullet combinations.
While it may be argued the 6 PPC is an "inherently accurate" cartridge on examination this does not hold true since its best accuracy comes only within a narrow range of velocity, bullet weights and powders which IMO opinion removes it from the "inherently accurate" list.
Perhaps, but within the narrow range it's more accurate than anything else. The question would be better defined as "Does cartridge design make a difference in accuracy?"
As you've pointed out, throughout shooting history there have been certain cartridges that have been the favorites of benchrest shooters. For a while it was the 222 Rem, then the 6mm PPC came along and became the cartridge of choice.
If cartridge design didn't make a difference in accuracy, this wouldn't happen. Benchrest shooters would use whatever cartridge struck their fancy and competitions would be won by dozens of different cartridges. This isn't what actually happens, almost all serious benchrest shooters use the same cartridge.
So cartridge design DOES make a difference. However the difference is small enough that it's only going to be noticeable in full out target guns.
