Through my 45 year handloading career, I always had the assumption that the Remington 405 grain was a softer (weaker, structurally) bullet than the Speer 400. I have held this opinion even after using both on deer and black bear, getting complete lung-shot pass throughs and not recovering either slug.
I decided to do an experiment
I placed each bullet on a piece of aluminum plate, centered them in a 5 foot section of 1 3/4" plastic pipe, held a 3 pound slug of 4140 over the other end, and let go.
Here's the setup:
Here's the result:
The impact to the Remington was caused by 5 drops
The impact to the Speer was caused by
3 drops I don't know what medium Speer used for that beautiful expansion test mushroom in their loading manual, but after this test, I'm fully convinced that it was room-temperature
butter.