The 56 is the gun with the "scope killer" reputation. It's the one where the barrel slides on a rail, so the stock stays stable during recoil - making it MUCH easier to shoot accurately. Unfortunately, it also means the weight of the stock doesn't dampen the recoil forces on the scope either. So the scope gets LOTS more recoil shock.
The 52 is the same as the 48, but with an upgraded stock that has checkering on the forearm, and a high check piece.
The barrel is firmly bolted on the stock, and does not slide on rails.
So the recoil of the 52 and 48 are no worse than any other magnum springer.
The 48 and 52 both definitely need a springer rated scope.
But any springer rated scope should be fine.
The 56 needs a springer rated scope with VERY robust lens holders.
The SWFA Super Sniper scopes and the Vortex Diamondback scope have good track records on the 56.