I had a few of the 7mm copper capped and lead nosed H-Mantle bullets, didn't get to try them so gave them away to a colleague who had made up a 7x57 stalker rifle and used heavier bullets. Had sectioned one of the copper caped bullets years ago just to see what they were like inside.
The H-Mantle construction is more like a Hornady interlock or Remington corelokt and not a Nosler partition where the base essentially becomes a solid once the nose portion has sloughed off.

I imagine the H-Mantle would continue with some expansion past the crimped jacket if hitting at a higher velocity in solid muscle or bone. The early H-Mantles such as that in the image below had a homogenous lead core whereas the later H-Mantles had a dual core, possible done to stop expansion past the jacket crimp.

Pre-80's 173gr 7mm H-Mantle