I don't think Sierra has changed the bullets they sell as components much if at all over the years. What they sell under contract with other companies might be another story. Rather than using any kinds of jacket rings or bonding to control expansion characteristics however, they rely soley, it seems, on jacket thickness and hardness/toughness together with core alloy and hardness to control expansion. I know both the 300 Gameking in .375 and the 250 Gameking in .338 (and 225 .358) have hard cores which make the bullets quite tough. They are however, malleable enough to act somewhat putty-like while in action. I have recovered or seen several that worked like that anyway.
This is one of two 250 .338s I've seen used on moose. This bullet appeared to be a well-expanded, intact slug when I pulled it out of the DRT bull (moose) it killed (at just over 200 yards). It was when I was washing it off that it came apart and I realized that the core had actually been 'feeding out' of the jacket as it expanded. I found the jacket of another of the same in the snow beyond another bull which I killed at around 400 yards. The core went on deeper into the drift where I couldn't find it. I hit that animal about 6 inches apart with two different 250 grainers - a Gameking and an Interlock while he stood in one spot. Both bullets penetrated the meaty area of the legs below the shoulders. The Interlock made it into the far side. The Gameking went all the way through.
I have had or seen similar results with the 300 .375. I generally prefer Interlocks simply because I have had better luck getting them to shoot well consistently in my hunting rifles. But there are a lot of ways to improve on either of them for hunting - which isn't to say that they can't get 'er done.