Note the “bimetal” jacket. Looks like copper but really is just a light plating of it. Scrap the copper off and it is steel - very soft. I have some WW1 7mm FMJ that is steel also. A good magnet will hold the bullet up off a table.
I stand partially corrected...still these are not stell jacketed but rather steel core with a copper jacket.....a steel jacket, even a “soft stell one would erode a barrel pretty quickly unless it was a smothbore.
The linked rounds appear to have enough copper on them to prevent erosion of the barrel’s rifling....