A non-bonded JHP may separate, but it is much more likely to do so when tested in water (or wet cloth/paper). Separation is bad because the bullet loses mass, and will not penetrate as far - the copper jacket is so light it will not do any damage by itself. It's not the end of the world. There are better bullets, but I believe the rangers work fine.
There have been some problems when shooting through glass, the copper jacket gets stuck and the rest of the bullet squeezes through, deformed, and moving much slower.