Yes, GameKings, Hot Cores, and other CnC Bullets will fail when used outside their design parameters.

Perhaps I could clarify my opinion by rephrasing to: IMO, it's prudent to use a bullet, or any product within its design parameters. Partitions, Accubonds, and other bullet designs, may, due to their construction, operate well over a wider velocity range.

And, yes, any bullet design can and will fail. But the failure rate, given a sufficient sample size, will be less for the product that is used as it's designed.