In the "olden days," J O'C and Elmer Keith used to brag about the Western Tool and Copper Works bullets in their favorite caliber, '06, 270, and 7mm. It's dependability was largely due to the large amount of lead exposed, but only because of the lower velocities in those cartridges. When faster cartridges came out, the bullets "exploded" and lost the ability to penetrate.
The BP and ST were to compete them. The jacket of the BP wasn't tapered and tended to thicken when drawn, so penetrated deeply, and needed to have the bronze wedge to initiate expansion so it wouldn't "pencil through." Often it wouldn't work, so would go on through, as with large bones.
STs were the large exposed tips with an aluminum cover, to retard expansion. It was difficult to manufacture a small tipped bullet with the little cover, so as velocities went up, the ST wasn't effective, so fell to the wayside.
In the '06 180 grain, .270 150 grain, 7x57 with 175 grain, and 7mm/06 with 160 and 175 grain, there were few combination that were as good for large deer, Elk, and Moose. That is where thse cartridges got their reps.
The last to go was the .30-30 with 170 grain STs. It was never expected to go fast, therefore worked very well. It was just too expensive to produce for only one loading.
In my "collection," I still have a 1/2 box or so of 180 STs, and a few less of 150 and 180 BPs, and several boxes of loaded .30/30 170 grainers, just in case I get to go hunting deer again, and decide to carry one of the old rifles, instead of a newer magnum.
Have fun,
Gene
