I used a fair amount of this stuff years ago. I agree that functioning in an SKS is inconsistent.
Some lots worked ok and I saved those for the young kids to shoot.
I was surprised that these would shoot through an 8" diameter tree trunk at close range. Even though the core is plastic, it's a very dense, HDPE like material.
I sectioned some of these for my collection but they are long gone and the pics I took were lost somehow.