A few comments:
First, I didn't object to the OPs question comparing the heavier-jacketed Ballistic Tips to Partitions--but as several have noted, they're not Partitions.
However, my experience with the .338 200-grain is very extensive--partly because they were the first heavy-jacket BTs. I actually started using them shortly before Nosler announced them, when the late Chub Eastman (then the writer contact for Nosler) asked me to try some in 1993.
The first thing I did after working up a handload (which was easy) was test their penetration by shooting one into the "media" I'd been using for a few years to test big game bullets, a stack of dry newspaper. I've listed the reasons for this choice both here and in articles and books, but one of its virtues is being able to shoot more than one type/brand of bullet into the same stack, to compare penetration depth. I did that with the 200 Ballistic Tips and 210 Partitions--and the Ballistic Tips penetrated 90% as deeply.
The first animal I took with one was a bull caribou in northern Quebec, which is still the biggest-bodied bull I've killed out of a dozen, about as large as a typical 5x5 bull elk. He was standing broadside at around 200 yards, with his near front hoof maybe a foot in front of the the far one, and I put the bullet in the little pocket behind the near leg.
At the shot the bull dropped straight down and never moved, legs already folded underneath him, ready for the trophy photo. The bullet scrambled the chest cavity and then broke the big joint of the far shoulder before exiting.
After that I used that load on a bunch of other game both in North America and Africa, and also gave some to local friends with .338s who took deer and elk with them. One used it on a 6x5 bull that was quartering away at around 150 yards. Same sort of deal: The bull dropped right there, partly because that bullet also broke the shoulder joint on the way out.
The only one that was recovered killed a gemsbok bull that was almost facing me at 150 yards. That one broke the near shoulder going in, and then took off the bottom of the spine before ending up under the hide of the rump on the opposite side. It retained 60% of its weight.
Our fellow member Shrapnel has killed more than one elk with the heavy-jacket .30, one a cow that stood facing him when he was carrying his .300 Weatherby. Can't remember whether it was 165-grain or 180-grain bullet, but that bullet also ended up under the hide of the rump.
No, they're not Partitions, but the heavy-jacket BTs are pretty stout bullets.
I've also discussed bullet construction with the Nosler folks at their plant in Bend, which I've visited several times over the decades. One thing they do is tweak construction of their bullets after they're introduced, sometimes more than once. They do use different lead alloys for the front and rear cores, and have been since the Partition appeared in 1948, but they don't always use the same lead alloys in Partitions of different calibers for the front and rear cores.
During one visit they told about how they'd recently tweaked the 300-grain .375 Partition (the later, extruded version that appeared around 1990) by not only using a harder rear core, but a thicker rear jacket. Both tweaks not only helped the bullet hold up when hitting heavy bone, but also resulted in smaller groups in their indoor range.
More than one other bullet company does the same sort of tweaking, or even massive redesigning as Barnes has done with their various X-Bullets over the decades. But companies that make more conventional lead-cores also often tweak them.
