Bullet's rebound: better plated or FMJ ?

[Stefano]

I would like to share your experiences about bullets's rebound:

shooting steels and/or toward a rock-backstop what's more dangerous: plated bullets or FMJ ones ??

Usually people thinks that lead (or copper-plated) bullets are much more safe because they are less subjected to rebounds, buy from my own experience I begin to think exactly the opposite ...

Shooting towards the same backstop, I've experienced A LOT of rebounds with copper-plated bullets, and a very fiew (or none) with full metal jacketed bullets ...

NOTE: I am shooting 9mm minor, and the differences I've verified are between:

A - 124grs RN copper-plated bullet (power factor 130) - FASTER

B - 147grs RN FMJ bullet (power factor 130) - SLOWER

Is it possible that the much more frequent rebounds I've noticed (A-type ammo) are due to the faster speed of the bullet ?

Even if the power factor is quite the same of the B-type ammo ??